Question 422690
I'm assuming you want to factor this.





{{{72x^3-11x^2-380x}}} Start with the given expression.



{{{x(72x^2-11x-380)}}} Factor out the GCF {{{x}}}.



Now let's try to factor the inner expression {{{72x^2-11x-380}}}



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Looking at the expression {{{72x^2-11x-380}}}, we can see that the first coefficient is {{{72}}}, the second coefficient is {{{-11}}}, and the last term is {{{-380}}}.



Now multiply the first coefficient {{{72}}} by the last term {{{-380}}} to get {{{(72)(-380)=-27360}}}.



Now the question is: what two whole numbers multiply to {{{-27360}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{-11}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{-27360}}} (the previous product).



Factors of {{{-27360}}}:

1,2,3,4,5,6,8,9,10,12,15,16,18,19,20,24,30,32,36,38,40,45,48,57,60,72,76,80,90,95,96,114,120,144,152,160,171,180,190,228,240,285,288,304,342,360,380,456,480,570,608,684,720,760,855,912,1140,1368,1440,1520,1710,1824,2280,2736,3040,3420,4560,5472,6840,9120,13680,27360

-1,-2,-3,-4,-5,-6,-8,-9,-10,-12,-15,-16,-18,-19,-20,-24,-30,-32,-36,-38,-40,-45,-48,-57,-60,-72,-76,-80,-90,-95,-96,-114,-120,-144,-152,-160,-171,-180,-190,-228,-240,-285,-288,-304,-342,-360,-380,-456,-480,-570,-608,-684,-720,-760,-855,-912,-1140,-1368,-1440,-1520,-1710,-1824,-2280,-2736,-3040,-3420,-4560,-5472,-6840,-9120,-13680,-27360



Note: list the negative of each factor. This will allow us to find all possible combinations.



These factors pair up and multiply to {{{-27360}}}.

1*(-27360) = -27360
2*(-13680) = -27360
3*(-9120) = -27360
4*(-6840) = -27360
5*(-5472) = -27360
6*(-4560) = -27360
8*(-3420) = -27360
9*(-3040) = -27360
10*(-2736) = -27360
12*(-2280) = -27360
15*(-1824) = -27360
16*(-1710) = -27360
18*(-1520) = -27360
19*(-1440) = -27360
20*(-1368) = -27360
24*(-1140) = -27360
30*(-912) = -27360
32*(-855) = -27360
36*(-760) = -27360
38*(-720) = -27360
40*(-684) = -27360
45*(-608) = -27360
48*(-570) = -27360
57*(-480) = -27360
60*(-456) = -27360
72*(-380) = -27360
76*(-360) = -27360
80*(-342) = -27360
90*(-304) = -27360
95*(-288) = -27360
96*(-285) = -27360
114*(-240) = -27360
120*(-228) = -27360
144*(-190) = -27360
152*(-180) = -27360
160*(-171) = -27360
(-1)*(27360) = -27360
(-2)*(13680) = -27360
(-3)*(9120) = -27360
(-4)*(6840) = -27360
(-5)*(5472) = -27360
(-6)*(4560) = -27360
(-8)*(3420) = -27360
(-9)*(3040) = -27360
(-10)*(2736) = -27360
(-12)*(2280) = -27360
(-15)*(1824) = -27360
(-16)*(1710) = -27360
(-18)*(1520) = -27360
(-19)*(1440) = -27360
(-20)*(1368) = -27360
(-24)*(1140) = -27360
(-30)*(912) = -27360
(-32)*(855) = -27360
(-36)*(760) = -27360
(-38)*(720) = -27360
(-40)*(684) = -27360
(-45)*(608) = -27360
(-48)*(570) = -27360
(-57)*(480) = -27360
(-60)*(456) = -27360
(-72)*(380) = -27360
(-76)*(360) = -27360
(-80)*(342) = -27360
(-90)*(304) = -27360
(-95)*(288) = -27360
(-96)*(285) = -27360
(-114)*(240) = -27360
(-120)*(228) = -27360
(-144)*(190) = -27360
(-152)*(180) = -27360
(-160)*(171) = -27360


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{-11}}}:



<table border="1"><th>First Number</th><th>Second Number</th><th>Sum</th><tr><td  align="center"><font color=black>1</font></td><td  align="center"><font color=black>-27360</font></td><td  align="center"><font color=black>1+(-27360)=-27359</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>-13680</font></td><td  align="center"><font color=black>2+(-13680)=-13678</font></td></tr><tr><td  align="center"><font color=black>3</font></td><td  align="center"><font color=black>-9120</font></td><td  align="center"><font color=black>3+(-9120)=-9117</font></td></tr><tr><td  align="center"><font color=black>4</font></td><td  align="center"><font color=black>-6840</font></td><td  align="center"><font color=black>4+(-6840)=-6836</font></td></tr><tr><td  align="center"><font color=black>5</font></td><td  align="center"><font color=black>-5472</font></td><td  align="center"><font color=black>5+(-5472)=-5467</font></td></tr><tr><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>-4560</font></td><td  align="center"><font color=black>6+(-4560)=-4554</font></td></tr><tr><td  align="center"><font color=black>8</font></td><td  align="center"><font color=black>-3420</font></td><td  align="center"><font color=black>8+(-3420)=-3412</font></td></tr><tr><td  align="center"><font color=black>9</font></td><td  align="center"><font color=black>-3040</font></td><td  align="center"><font color=black>9+(-3040)=-3031</font></td></tr><tr><td  align="center"><font color=black>10</font></td><td  align="center"><font color=black>-2736</font></td><td  align="center"><font color=black>10+(-2736)=-2726</font></td></tr><tr><td  align="center"><font color=black>12</font></td><td  align="center"><font color=black>-2280</font></td><td  align="center"><font color=black>12+(-2280)=-2268</font></td></tr><tr><td  align="center"><font color=black>15</font></td><td  align="center"><font color=black>-1824</font></td><td  align="center"><font color=black>15+(-1824)=-1809</font></td></tr><tr><td  align="center"><font color=black>16</font></td><td  align="center"><font color=black>-1710</font></td><td  align="center"><font color=black>16+(-1710)=-1694</font></td></tr><tr><td  align="center"><font color=black>18</font></td><td  align="center"><font color=black>-1520</font></td><td  align="center"><font color=black>18+(-1520)=-1502</font></td></tr><tr><td  align="center"><font color=black>19</font></td><td  align="center"><font color=black>-1440</font></td><td  align="center"><font color=black>19+(-1440)=-1421</font></td></tr><tr><td  align="center"><font color=black>20</font></td><td  align="center"><font color=black>-1368</font></td><td  align="center"><font color=black>20+(-1368)=-1348</font></td></tr><tr><td  align="center"><font color=black>24</font></td><td  align="center"><font color=black>-1140</font></td><td  align="center"><font color=black>24+(-1140)=-1116</font></td></tr><tr><td  align="center"><font color=black>30</font></td><td  align="center"><font color=black>-912</font></td><td  align="center"><font color=black>30+(-912)=-882</font></td></tr><tr><td  align="center"><font color=black>32</font></td><td  align="center"><font color=black>-855</font></td><td  align="center"><font color=black>32+(-855)=-823</font></td></tr><tr><td  align="center"><font color=black>36</font></td><td  align="center"><font color=black>-760</font></td><td  align="center"><font color=black>36+(-760)=-724</font></td></tr><tr><td  align="center"><font color=black>38</font></td><td  align="center"><font color=black>-720</font></td><td  align="center"><font color=black>38+(-720)=-682</font></td></tr><tr><td  align="center"><font color=black>40</font></td><td  align="center"><font color=black>-684</font></td><td  align="center"><font color=black>40+(-684)=-644</font></td></tr><tr><td  align="center"><font color=black>45</font></td><td  align="center"><font color=black>-608</font></td><td  align="center"><font color=black>45+(-608)=-563</font></td></tr><tr><td  align="center"><font color=black>48</font></td><td  align="center"><font color=black>-570</font></td><td  align="center"><font color=black>48+(-570)=-522</font></td></tr><tr><td  align="center"><font color=black>57</font></td><td  align="center"><font color=black>-480</font></td><td  align="center"><font color=black>57+(-480)=-423</font></td></tr><tr><td  align="center"><font color=black>60</font></td><td  align="center"><font color=black>-456</font></td><td  align="center"><font color=black>60+(-456)=-396</font></td></tr><tr><td  align="center"><font color=black>72</font></td><td  align="center"><font color=black>-380</font></td><td  align="center"><font color=black>72+(-380)=-308</font></td></tr><tr><td  align="center"><font color=black>76</font></td><td  align="center"><font color=black>-360</font></td><td  align="center"><font color=black>76+(-360)=-284</font></td></tr><tr><td  align="center"><font color=black>80</font></td><td  align="center"><font color=black>-342</font></td><td  align="center"><font color=black>80+(-342)=-262</font></td></tr><tr><td  align="center"><font color=black>90</font></td><td  align="center"><font color=black>-304</font></td><td  align="center"><font color=black>90+(-304)=-214</font></td></tr><tr><td  align="center"><font color=black>95</font></td><td  align="center"><font color=black>-288</font></td><td  align="center"><font color=black>95+(-288)=-193</font></td></tr><tr><td  align="center"><font color=black>96</font></td><td  align="center"><font color=black>-285</font></td><td  align="center"><font color=black>96+(-285)=-189</font></td></tr><tr><td  align="center"><font color=black>114</font></td><td  align="center"><font color=black>-240</font></td><td  align="center"><font color=black>114+(-240)=-126</font></td></tr><tr><td  align="center"><font color=black>120</font></td><td  align="center"><font color=black>-228</font></td><td  align="center"><font color=black>120+(-228)=-108</font></td></tr><tr><td  align="center"><font color=black>144</font></td><td  align="center"><font color=black>-190</font></td><td  align="center"><font color=black>144+(-190)=-46</font></td></tr><tr><td  align="center"><font color=black>152</font></td><td  align="center"><font color=black>-180</font></td><td  align="center"><font color=black>152+(-180)=-28</font></td></tr><tr><td  align="center"><font color=red>160</font></td><td  align="center"><font color=red>-171</font></td><td  align="center"><font color=red>160+(-171)=-11</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>27360</font></td><td  align="center"><font color=black>-1+27360=27359</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>13680</font></td><td  align="center"><font color=black>-2+13680=13678</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>9120</font></td><td  align="center"><font color=black>-3+9120=9117</font></td></tr><tr><td  align="center"><font color=black>-4</font></td><td  align="center"><font color=black>6840</font></td><td  align="center"><font color=black>-4+6840=6836</font></td></tr><tr><td  align="center"><font color=black>-5</font></td><td  align="center"><font color=black>5472</font></td><td  align="center"><font color=black>-5+5472=5467</font></td></tr><tr><td  align="center"><font color=black>-6</font></td><td  align="center"><font color=black>4560</font></td><td  align="center"><font color=black>-6+4560=4554</font></td></tr><tr><td  align="center"><font color=black>-8</font></td><td  align="center"><font color=black>3420</font></td><td  align="center"><font color=black>-8+3420=3412</font></td></tr><tr><td  align="center"><font color=black>-9</font></td><td  align="center"><font color=black>3040</font></td><td  align="center"><font color=black>-9+3040=3031</font></td></tr><tr><td  align="center"><font color=black>-10</font></td><td  align="center"><font color=black>2736</font></td><td  align="center"><font color=black>-10+2736=2726</font></td></tr><tr><td  align="center"><font color=black>-12</font></td><td  align="center"><font color=black>2280</font></td><td  align="center"><font color=black>-12+2280=2268</font></td></tr><tr><td  align="center"><font color=black>-15</font></td><td  align="center"><font color=black>1824</font></td><td  align="center"><font color=black>-15+1824=1809</font></td></tr><tr><td  align="center"><font color=black>-16</font></td><td  align="center"><font color=black>1710</font></td><td  align="center"><font color=black>-16+1710=1694</font></td></tr><tr><td  align="center"><font color=black>-18</font></td><td  align="center"><font color=black>1520</font></td><td  align="center"><font color=black>-18+1520=1502</font></td></tr><tr><td  align="center"><font color=black>-19</font></td><td  align="center"><font color=black>1440</font></td><td  align="center"><font color=black>-19+1440=1421</font></td></tr><tr><td  align="center"><font color=black>-20</font></td><td  align="center"><font color=black>1368</font></td><td  align="center"><font color=black>-20+1368=1348</font></td></tr><tr><td  align="center"><font color=black>-24</font></td><td  align="center"><font color=black>1140</font></td><td  align="center"><font color=black>-24+1140=1116</font></td></tr><tr><td  align="center"><font color=black>-30</font></td><td  align="center"><font color=black>912</font></td><td  align="center"><font color=black>-30+912=882</font></td></tr><tr><td  align="center"><font color=black>-32</font></td><td  align="center"><font color=black>855</font></td><td  align="center"><font color=black>-32+855=823</font></td></tr><tr><td  align="center"><font color=black>-36</font></td><td  align="center"><font color=black>760</font></td><td  align="center"><font color=black>-36+760=724</font></td></tr><tr><td  align="center"><font color=black>-38</font></td><td  align="center"><font color=black>720</font></td><td  align="center"><font color=black>-38+720=682</font></td></tr><tr><td  align="center"><font color=black>-40</font></td><td  align="center"><font color=black>684</font></td><td  align="center"><font color=black>-40+684=644</font></td></tr><tr><td  align="center"><font color=black>-45</font></td><td  align="center"><font color=black>608</font></td><td  align="center"><font color=black>-45+608=563</font></td></tr><tr><td  align="center"><font color=black>-48</font></td><td  align="center"><font color=black>570</font></td><td  align="center"><font color=black>-48+570=522</font></td></tr><tr><td  align="center"><font color=black>-57</font></td><td  align="center"><font color=black>480</font></td><td  align="center"><font color=black>-57+480=423</font></td></tr><tr><td  align="center"><font color=black>-60</font></td><td  align="center"><font color=black>456</font></td><td  align="center"><font color=black>-60+456=396</font></td></tr><tr><td  align="center"><font color=black>-72</font></td><td  align="center"><font color=black>380</font></td><td  align="center"><font color=black>-72+380=308</font></td></tr><tr><td  align="center"><font color=black>-76</font></td><td  align="center"><font color=black>360</font></td><td  align="center"><font color=black>-76+360=284</font></td></tr><tr><td  align="center"><font color=black>-80</font></td><td  align="center"><font color=black>342</font></td><td  align="center"><font color=black>-80+342=262</font></td></tr><tr><td  align="center"><font color=black>-90</font></td><td  align="center"><font color=black>304</font></td><td  align="center"><font color=black>-90+304=214</font></td></tr><tr><td  align="center"><font color=black>-95</font></td><td  align="center"><font color=black>288</font></td><td  align="center"><font color=black>-95+288=193</font></td></tr><tr><td  align="center"><font color=black>-96</font></td><td  align="center"><font color=black>285</font></td><td  align="center"><font color=black>-96+285=189</font></td></tr><tr><td  align="center"><font color=black>-114</font></td><td  align="center"><font color=black>240</font></td><td  align="center"><font color=black>-114+240=126</font></td></tr><tr><td  align="center"><font color=black>-120</font></td><td  align="center"><font color=black>228</font></td><td  align="center"><font color=black>-120+228=108</font></td></tr><tr><td  align="center"><font color=black>-144</font></td><td  align="center"><font color=black>190</font></td><td  align="center"><font color=black>-144+190=46</font></td></tr><tr><td  align="center"><font color=black>-152</font></td><td  align="center"><font color=black>180</font></td><td  align="center"><font color=black>-152+180=28</font></td></tr><tr><td  align="center"><font color=black>-160</font></td><td  align="center"><font color=black>171</font></td><td  align="center"><font color=black>-160+171=11</font></td></tr></table>



From the table, we can see that the two numbers {{{160}}} and {{{-171}}} add to {{{-11}}} (the middle coefficient).



So the two numbers {{{160}}} and {{{-171}}} both multiply to {{{-27360}}} <font size=4><b>and</b></font> add to {{{-11}}}



Now replace the middle term {{{-11x}}} with {{{160x-171x}}}. Remember, {{{160}}} and {{{-171}}} add to {{{-11}}}. So this shows us that {{{160x-171x=-11x}}}.



{{{72x^2+highlight(160x-171x)-380}}} Replace the second term {{{-11x}}} with {{{160x-171x}}}.



{{{(72x^2+160x)+(-171x-380)}}} Group the terms into two pairs.



{{{8x(9x+20)+(-171x-380)}}} Factor out the GCF {{{8x}}} from the first group.



{{{8x(9x+20)-19(9x+20)}}} Factor out {{{19}}} from the second group. The goal of this step is to make the terms in the second parenthesis equal to the terms in the first parenthesis.



{{{(8x-19)(9x+20)}}} Combine like terms. Or factor out the common term {{{9x+20}}}



--------------------------------------------------



So {{{x(72x^2-11x-380)}}} then factors further to {{{x(8x-19)(9x+20)}}}



===============================================================



Answer:



So {{{72x^3-11x^2-380x}}} completely factors to {{{x(8x-19)(9x+20)}}}.



In other words, {{{72x^3-11x^2-380x=x(8x-19)(9x+20)}}}.



Note: you can check the answer by expanding {{{x(8x-19)(9x+20)}}} to get {{{72x^3-11x^2-380x}}} or by graphing the original expression and the answer (the two graphs should be identical).



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