Question 207384

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Looking at the expression {{{54t^2+3t-70}}}, we can see that the first coefficient is {{{54}}}, the second coefficient is {{{3}}}, and the last term is {{{-70}}}.



Now multiply the first coefficient {{{54}}} by the last term {{{-70}}} to get {{{(54)(-70)=-3780}}}.



Now the question is: what two whole numbers multiply to {{{-3780}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{3}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{-3780}}} (the previous product).



Factors of {{{-3780}}}:

1,2,3,4,5,6,7,9,10,12,14,15,18,20,21,27,28,30,35,36,42,45,54,60,63,70,84,90,105,108,126,135,140,180,189,210,252,270,315,378,420,540,630,756,945,1260,1890,3780

-1,-2,-3,-4,-5,-6,-7,-9,-10,-12,-14,-15,-18,-20,-21,-27,-28,-30,-35,-36,-42,-45,-54,-60,-63,-70,-84,-90,-105,-108,-126,-135,-140,-180,-189,-210,-252,-270,-315,-378,-420,-540,-630,-756,-945,-1260,-1890,-3780



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



These factors pair up and multiply to {{{-3780}}}.

1*(-3780) = -3780
2*(-1890) = -3780
3*(-1260) = -3780
4*(-945) = -3780
5*(-756) = -3780
6*(-630) = -3780
7*(-540) = -3780
9*(-420) = -3780
10*(-378) = -3780
12*(-315) = -3780
14*(-270) = -3780
15*(-252) = -3780
18*(-210) = -3780
20*(-189) = -3780
21*(-180) = -3780
27*(-140) = -3780
28*(-135) = -3780
30*(-126) = -3780
35*(-108) = -3780
36*(-105) = -3780
42*(-90) = -3780
45*(-84) = -3780
54*(-70) = -3780
60*(-63) = -3780
(-1)*(3780) = -3780
(-2)*(1890) = -3780
(-3)*(1260) = -3780
(-4)*(945) = -3780
(-5)*(756) = -3780
(-6)*(630) = -3780
(-7)*(540) = -3780
(-9)*(420) = -3780
(-10)*(378) = -3780
(-12)*(315) = -3780
(-14)*(270) = -3780
(-15)*(252) = -3780
(-18)*(210) = -3780
(-20)*(189) = -3780
(-21)*(180) = -3780
(-27)*(140) = -3780
(-28)*(135) = -3780
(-30)*(126) = -3780
(-35)*(108) = -3780
(-36)*(105) = -3780
(-42)*(90) = -3780
(-45)*(84) = -3780
(-54)*(70) = -3780
(-60)*(63) = -3780


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{3}}}:



<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>-3780</font></td><td  align="center"><font color=black>1+(-3780)=-3779</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>-1890</font></td><td  align="center"><font color=black>2+(-1890)=-1888</font></td></tr><tr><td  align="center"><font color=black>3</font></td><td  align="center"><font color=black>-1260</font></td><td  align="center"><font color=black>3+(-1260)=-1257</font></td></tr><tr><td  align="center"><font color=black>4</font></td><td  align="center"><font color=black>-945</font></td><td  align="center"><font color=black>4+(-945)=-941</font></td></tr><tr><td  align="center"><font color=black>5</font></td><td  align="center"><font color=black>-756</font></td><td  align="center"><font color=black>5+(-756)=-751</font></td></tr><tr><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>-630</font></td><td  align="center"><font color=black>6+(-630)=-624</font></td></tr><tr><td  align="center"><font color=black>7</font></td><td  align="center"><font color=black>-540</font></td><td  align="center"><font color=black>7+(-540)=-533</font></td></tr><tr><td  align="center"><font color=black>9</font></td><td  align="center"><font color=black>-420</font></td><td  align="center"><font color=black>9+(-420)=-411</font></td></tr><tr><td  align="center"><font color=black>10</font></td><td  align="center"><font color=black>-378</font></td><td  align="center"><font color=black>10+(-378)=-368</font></td></tr><tr><td  align="center"><font color=black>12</font></td><td  align="center"><font color=black>-315</font></td><td  align="center"><font color=black>12+(-315)=-303</font></td></tr><tr><td  align="center"><font color=black>14</font></td><td  align="center"><font color=black>-270</font></td><td  align="center"><font color=black>14+(-270)=-256</font></td></tr><tr><td  align="center"><font color=black>15</font></td><td  align="center"><font color=black>-252</font></td><td  align="center"><font color=black>15+(-252)=-237</font></td></tr><tr><td  align="center"><font color=black>18</font></td><td  align="center"><font color=black>-210</font></td><td  align="center"><font color=black>18+(-210)=-192</font></td></tr><tr><td  align="center"><font color=black>20</font></td><td  align="center"><font color=black>-189</font></td><td  align="center"><font color=black>20+(-189)=-169</font></td></tr><tr><td  align="center"><font color=black>21</font></td><td  align="center"><font color=black>-180</font></td><td  align="center"><font color=black>21+(-180)=-159</font></td></tr><tr><td  align="center"><font color=black>27</font></td><td  align="center"><font color=black>-140</font></td><td  align="center"><font color=black>27+(-140)=-113</font></td></tr><tr><td  align="center"><font color=black>28</font></td><td  align="center"><font color=black>-135</font></td><td  align="center"><font color=black>28+(-135)=-107</font></td></tr><tr><td  align="center"><font color=black>30</font></td><td  align="center"><font color=black>-126</font></td><td  align="center"><font color=black>30+(-126)=-96</font></td></tr><tr><td  align="center"><font color=black>35</font></td><td  align="center"><font color=black>-108</font></td><td  align="center"><font color=black>35+(-108)=-73</font></td></tr><tr><td  align="center"><font color=black>36</font></td><td  align="center"><font color=black>-105</font></td><td  align="center"><font color=black>36+(-105)=-69</font></td></tr><tr><td  align="center"><font color=black>42</font></td><td  align="center"><font color=black>-90</font></td><td  align="center"><font color=black>42+(-90)=-48</font></td></tr><tr><td  align="center"><font color=black>45</font></td><td  align="center"><font color=black>-84</font></td><td  align="center"><font color=black>45+(-84)=-39</font></td></tr><tr><td  align="center"><font color=black>54</font></td><td  align="center"><font color=black>-70</font></td><td  align="center"><font color=black>54+(-70)=-16</font></td></tr><tr><td  align="center"><font color=black>60</font></td><td  align="center"><font color=black>-63</font></td><td  align="center"><font color=black>60+(-63)=-3</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>3780</font></td><td  align="center"><font color=black>-1+3780=3779</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>1890</font></td><td  align="center"><font color=black>-2+1890=1888</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>1260</font></td><td  align="center"><font color=black>-3+1260=1257</font></td></tr><tr><td  align="center"><font color=black>-4</font></td><td  align="center"><font color=black>945</font></td><td  align="center"><font color=black>-4+945=941</font></td></tr><tr><td  align="center"><font color=black>-5</font></td><td  align="center"><font color=black>756</font></td><td  align="center"><font color=black>-5+756=751</font></td></tr><tr><td  align="center"><font color=black>-6</font></td><td  align="center"><font color=black>630</font></td><td  align="center"><font color=black>-6+630=624</font></td></tr><tr><td  align="center"><font color=black>-7</font></td><td  align="center"><font color=black>540</font></td><td  align="center"><font color=black>-7+540=533</font></td></tr><tr><td  align="center"><font color=black>-9</font></td><td  align="center"><font color=black>420</font></td><td  align="center"><font color=black>-9+420=411</font></td></tr><tr><td  align="center"><font color=black>-10</font></td><td  align="center"><font color=black>378</font></td><td  align="center"><font color=black>-10+378=368</font></td></tr><tr><td  align="center"><font color=black>-12</font></td><td  align="center"><font color=black>315</font></td><td  align="center"><font color=black>-12+315=303</font></td></tr><tr><td  align="center"><font color=black>-14</font></td><td  align="center"><font color=black>270</font></td><td  align="center"><font color=black>-14+270=256</font></td></tr><tr><td  align="center"><font color=black>-15</font></td><td  align="center"><font color=black>252</font></td><td  align="center"><font color=black>-15+252=237</font></td></tr><tr><td  align="center"><font color=black>-18</font></td><td  align="center"><font color=black>210</font></td><td  align="center"><font color=black>-18+210=192</font></td></tr><tr><td  align="center"><font color=black>-20</font></td><td  align="center"><font color=black>189</font></td><td  align="center"><font color=black>-20+189=169</font></td></tr><tr><td  align="center"><font color=black>-21</font></td><td  align="center"><font color=black>180</font></td><td  align="center"><font color=black>-21+180=159</font></td></tr><tr><td  align="center"><font color=black>-27</font></td><td  align="center"><font color=black>140</font></td><td  align="center"><font color=black>-27+140=113</font></td></tr><tr><td  align="center"><font color=black>-28</font></td><td  align="center"><font color=black>135</font></td><td  align="center"><font color=black>-28+135=107</font></td></tr><tr><td  align="center"><font color=black>-30</font></td><td  align="center"><font color=black>126</font></td><td  align="center"><font color=black>-30+126=96</font></td></tr><tr><td  align="center"><font color=black>-35</font></td><td  align="center"><font color=black>108</font></td><td  align="center"><font color=black>-35+108=73</font></td></tr><tr><td  align="center"><font color=black>-36</font></td><td  align="center"><font color=black>105</font></td><td  align="center"><font color=black>-36+105=69</font></td></tr><tr><td  align="center"><font color=black>-42</font></td><td  align="center"><font color=black>90</font></td><td  align="center"><font color=black>-42+90=48</font></td></tr><tr><td  align="center"><font color=black>-45</font></td><td  align="center"><font color=black>84</font></td><td  align="center"><font color=black>-45+84=39</font></td></tr><tr><td  align="center"><font color=black>-54</font></td><td  align="center"><font color=black>70</font></td><td  align="center"><font color=black>-54+70=16</font></td></tr><tr><td  align="center"><font color=red>-60</font></td><td  align="center"><font color=red>63</font></td><td  align="center"><font color=red>-60+63=3</font></td></tr></table>



From the table, we can see that the two numbers {{{-60}}} and {{{63}}} add to {{{3}}} (the middle coefficient).



So the two numbers {{{-60}}} and {{{63}}} both multiply to {{{-3780}}} <font size=4><b>and</b></font> add to {{{3}}}



Now replace the middle term {{{3t}}} with {{{-60t+63t}}}. Remember, {{{-60}}} and {{{63}}} add to {{{3}}}. So this shows us that {{{-60t+63t=3t}}}.



{{{54t^2+highlight(-60t+63t)-70}}} Replace the second term {{{3t}}} with {{{-60t+63t}}}.



{{{(54t^2-60t)+(63t-70)}}} Group the terms into two pairs.



{{{6t(9t-10)+(63t-70)}}} Factor out the GCF {{{6t}}} from the first group.



{{{6t(9t-10)+7(9t-10)}}} Factor out {{{7}}} 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.



{{{(6t+7)(9t-10)}}} Combine like terms. Or factor out the common term {{{9t-10}}}



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Answer:



So {{{54t^2+3t-70}}} factors to {{{(6t+7)(9t-10)}}}.



In other words, {{{54t^2+3t-70=(6t+7)(9t-10)}}}.



Note: you can check the answer by expanding {{{(6t+7)(9t-10)}}} to get {{{54t^2+3t-70}}} or by graphing the original expression and the answer (the two graphs should be identical).


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