Question 565246


Looking at the expression {{{18p^2+9p-14}}}, we can see that the first coefficient is {{{18}}}, the second coefficient is {{{9}}}, and the last term is {{{-14}}}.



Now multiply the first coefficient {{{18}}} by the last term {{{-14}}} to get {{{(18)(-14)=-252}}}.



Now the question is: what two whole numbers multiply to {{{-252}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{9}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{-252}}} (the previous product).



Factors of {{{-252}}}:

1,2,3,4,6,7,9,12,14,18,21,28,36,42,63,84,126,252

-1,-2,-3,-4,-6,-7,-9,-12,-14,-18,-21,-28,-36,-42,-63,-84,-126,-252



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



These factors pair up and multiply to {{{-252}}}.

1*(-252) = -252
2*(-126) = -252
3*(-84) = -252
4*(-63) = -252
6*(-42) = -252
7*(-36) = -252
9*(-28) = -252
12*(-21) = -252
14*(-18) = -252
(-1)*(252) = -252
(-2)*(126) = -252
(-3)*(84) = -252
(-4)*(63) = -252
(-6)*(42) = -252
(-7)*(36) = -252
(-9)*(28) = -252
(-12)*(21) = -252
(-14)*(18) = -252


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{9}}}:



<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>-252</font></td><td  align="center"><font color=black>1+(-252)=-251</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>-126</font></td><td  align="center"><font color=black>2+(-126)=-124</font></td></tr><tr><td  align="center"><font color=black>3</font></td><td  align="center"><font color=black>-84</font></td><td  align="center"><font color=black>3+(-84)=-81</font></td></tr><tr><td  align="center"><font color=black>4</font></td><td  align="center"><font color=black>-63</font></td><td  align="center"><font color=black>4+(-63)=-59</font></td></tr><tr><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>-42</font></td><td  align="center"><font color=black>6+(-42)=-36</font></td></tr><tr><td  align="center"><font color=black>7</font></td><td  align="center"><font color=black>-36</font></td><td  align="center"><font color=black>7+(-36)=-29</font></td></tr><tr><td  align="center"><font color=black>9</font></td><td  align="center"><font color=black>-28</font></td><td  align="center"><font color=black>9+(-28)=-19</font></td></tr><tr><td  align="center"><font color=black>12</font></td><td  align="center"><font color=black>-21</font></td><td  align="center"><font color=black>12+(-21)=-9</font></td></tr><tr><td  align="center"><font color=black>14</font></td><td  align="center"><font color=black>-18</font></td><td  align="center"><font color=black>14+(-18)=-4</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>252</font></td><td  align="center"><font color=black>-1+252=251</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>126</font></td><td  align="center"><font color=black>-2+126=124</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>84</font></td><td  align="center"><font color=black>-3+84=81</font></td></tr><tr><td  align="center"><font color=black>-4</font></td><td  align="center"><font color=black>63</font></td><td  align="center"><font color=black>-4+63=59</font></td></tr><tr><td  align="center"><font color=black>-6</font></td><td  align="center"><font color=black>42</font></td><td  align="center"><font color=black>-6+42=36</font></td></tr><tr><td  align="center"><font color=black>-7</font></td><td  align="center"><font color=black>36</font></td><td  align="center"><font color=black>-7+36=29</font></td></tr><tr><td  align="center"><font color=black>-9</font></td><td  align="center"><font color=black>28</font></td><td  align="center"><font color=black>-9+28=19</font></td></tr><tr><td  align="center"><font color=red>-12</font></td><td  align="center"><font color=red>21</font></td><td  align="center"><font color=red>-12+21=9</font></td></tr><tr><td  align="center"><font color=black>-14</font></td><td  align="center"><font color=black>18</font></td><td  align="center"><font color=black>-14+18=4</font></td></tr></table>



From the table, we can see that the two numbers {{{-12}}} and {{{21}}} add to {{{9}}} (the middle coefficient).



So the two numbers {{{-12}}} and {{{21}}} both multiply to {{{-252}}} <font size=4><b>and</b></font> add to {{{9}}}



Now replace the middle term {{{9p}}} with {{{-12p+21p}}}. Remember, {{{-12}}} and {{{21}}} add to {{{9}}}. So this shows us that {{{-12p+21p=9p}}}.



{{{18p^2+highlight(-12p+21p)-14}}} Replace the second term {{{9p}}} with {{{-12p+21p}}}.



{{{(18p^2-12p)+(21p-14)}}} Group the terms into two pairs.



{{{6p(3p-2)+(21p-14)}}} Factor out the GCF {{{6p}}} from the first group.



{{{6p(3p-2)+7(3p-2)}}} 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.



{{{(6p+7)(3p-2)}}} Combine like terms. Or factor out the common term {{{3p-2}}}



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



Answer:



So {{{18p^2+9p-14}}} factors to {{{(6p+7)(3p-2)}}}.



In other words, {{{18p^2+9p-14=(6p+7)(3p-2)}}}.



Note: you can check the answer by expanding {{{(6p+7)(3p-2)}}} to get {{{18p^2+9p-14}}} or by graphing the original expression and the answer (the two graphs should be identical).

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