Question 345301
I'll help you factor. I'll let you take over after that.





Looking at the expression {{{4x^2+29x+30}}}, we can see that the first coefficient is {{{4}}}, the second coefficient is {{{29}}}, and the last term is {{{30}}}.



Now multiply the first coefficient {{{4}}} by the last term {{{30}}} to get {{{(4)(30)=120}}}.



Now the question is: what two whole numbers multiply to {{{120}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{29}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{120}}} (the previous product).



Factors of {{{120}}}:

1,2,3,4,5,6,8,10,12,15,20,24,30,40,60,120

-1,-2,-3,-4,-5,-6,-8,-10,-12,-15,-20,-24,-30,-40,-60,-120



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



These factors pair up and multiply to {{{120}}}.

1*120 = 120
2*60 = 120
3*40 = 120
4*30 = 120
5*24 = 120
6*20 = 120
8*15 = 120
10*12 = 120
(-1)*(-120) = 120
(-2)*(-60) = 120
(-3)*(-40) = 120
(-4)*(-30) = 120
(-5)*(-24) = 120
(-6)*(-20) = 120
(-8)*(-15) = 120
(-10)*(-12) = 120


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{29}}}:



<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>120</font></td><td  align="center"><font color=black>1+120=121</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>60</font></td><td  align="center"><font color=black>2+60=62</font></td></tr><tr><td  align="center"><font color=black>3</font></td><td  align="center"><font color=black>40</font></td><td  align="center"><font color=black>3+40=43</font></td></tr><tr><td  align="center"><font color=black>4</font></td><td  align="center"><font color=black>30</font></td><td  align="center"><font color=black>4+30=34</font></td></tr><tr><td  align="center"><font color=red>5</font></td><td  align="center"><font color=red>24</font></td><td  align="center"><font color=red>5+24=29</font></td></tr><tr><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>20</font></td><td  align="center"><font color=black>6+20=26</font></td></tr><tr><td  align="center"><font color=black>8</font></td><td  align="center"><font color=black>15</font></td><td  align="center"><font color=black>8+15=23</font></td></tr><tr><td  align="center"><font color=black>10</font></td><td  align="center"><font color=black>12</font></td><td  align="center"><font color=black>10+12=22</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>-120</font></td><td  align="center"><font color=black>-1+(-120)=-121</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>-60</font></td><td  align="center"><font color=black>-2+(-60)=-62</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>-40</font></td><td  align="center"><font color=black>-3+(-40)=-43</font></td></tr><tr><td  align="center"><font color=black>-4</font></td><td  align="center"><font color=black>-30</font></td><td  align="center"><font color=black>-4+(-30)=-34</font></td></tr><tr><td  align="center"><font color=black>-5</font></td><td  align="center"><font color=black>-24</font></td><td  align="center"><font color=black>-5+(-24)=-29</font></td></tr><tr><td  align="center"><font color=black>-6</font></td><td  align="center"><font color=black>-20</font></td><td  align="center"><font color=black>-6+(-20)=-26</font></td></tr><tr><td  align="center"><font color=black>-8</font></td><td  align="center"><font color=black>-15</font></td><td  align="center"><font color=black>-8+(-15)=-23</font></td></tr><tr><td  align="center"><font color=black>-10</font></td><td  align="center"><font color=black>-12</font></td><td  align="center"><font color=black>-10+(-12)=-22</font></td></tr></table>



From the table, we can see that the two numbers {{{5}}} and {{{24}}} add to {{{29}}} (the middle coefficient).



So the two numbers {{{5}}} and {{{24}}} both multiply to {{{120}}} <font size=4><b>and</b></font> add to {{{29}}}



Now replace the middle term {{{29x}}} with {{{5x+24x}}}. Remember, {{{5}}} and {{{24}}} add to {{{29}}}. So this shows us that {{{5x+24x=29x}}}.



{{{4x^2+highlight(5x+24x)+30}}} Replace the second term {{{29x}}} with {{{5x+24x}}}.



{{{(4x^2+5x)+(24x+30)}}} Group the terms into two pairs.



{{{x(4x+5)+(24x+30)}}} Factor out the GCF {{{x}}} from the first group.



{{{x(4x+5)+6(4x+5)}}} Factor out {{{6}}} 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.



{{{(x+6)(4x+5)}}} Combine like terms. Or factor out the common term {{{4x+5}}}



So {{{4x^2+29x+30}}} factors to {{{(x+6)(4x+5)}}}.



In other words, {{{4x^2+29x+30=(x+6)(4x+5)}}}.



Note: you can check the answer by expanding {{{(x+6)(4x+5)}}} to get {{{4x^2+29x+30}}} or by graphing the original expression and the answer (the two graphs should be identical).



If you need more help, email me at <a href="mailto:jim_thompson5910@hotmail.com?Subject=Algebra%20Help">jim_thompson5910@hotmail.com</a>


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Jim