Question 473453


Looking at the expression {{{2x^2+11x+12}}}, we can see that the first coefficient is {{{2}}}, the second coefficient is {{{11}}}, and the last term is {{{12}}}.



Now multiply the first coefficient {{{2}}} by the last term {{{12}}} to get {{{(2)(12)=24}}}.



Now the question is: what two whole numbers multiply to {{{24}}} (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 {{{24}}} (the previous product).



Factors of {{{24}}}:

1,2,3,4,6,8,12,24

-1,-2,-3,-4,-6,-8,-12,-24



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



These factors pair up and multiply to {{{24}}}.

1*24 = 24
2*12 = 24
3*8 = 24
4*6 = 24
(-1)*(-24) = 24
(-2)*(-12) = 24
(-3)*(-8) = 24
(-4)*(-6) = 24


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>24</font></td><td  align="center"><font color=black>1+24=25</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>12</font></td><td  align="center"><font color=black>2+12=14</font></td></tr><tr><td  align="center"><font color=red>3</font></td><td  align="center"><font color=red>8</font></td><td  align="center"><font color=red>3+8=11</font></td></tr><tr><td  align="center"><font color=black>4</font></td><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>4+6=10</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>-24</font></td><td  align="center"><font color=black>-1+(-24)=-25</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>-12</font></td><td  align="center"><font color=black>-2+(-12)=-14</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>-8</font></td><td  align="center"><font color=black>-3+(-8)=-11</font></td></tr><tr><td  align="center"><font color=black>-4</font></td><td  align="center"><font color=black>-6</font></td><td  align="center"><font color=black>-4+(-6)=-10</font></td></tr></table>



From the table, we can see that the two numbers {{{3}}} and {{{8}}} add to {{{11}}} (the middle coefficient).



So the two numbers {{{3}}} and {{{8}}} both multiply to {{{24}}} <font size=4><b>and</b></font> add to {{{11}}}



Now replace the middle term {{{11x}}} with {{{3x+8x}}}. Remember, {{{3}}} and {{{8}}} add to {{{11}}}. So this shows us that {{{3x+8x=11x}}}.



{{{2x^2+highlight(3x+8x)+12}}} Replace the second term {{{11x}}} with {{{3x+8x}}}.



{{{(2x^2+3x)+(8x+12)}}} Group the terms into two pairs.



{{{x(2x+3)+(8x+12)}}} Factor out the GCF {{{x}}} from the first group.



{{{x(2x+3)+4(2x+3)}}} Factor out {{{4}}} 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+4)(2x+3)}}} Combine like terms. Or factor out the common term {{{2x+3}}}



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Answer:



So {{{2x^2+11x+12}}} factors to {{{(x+4)(2x+3)}}}.



In other words, {{{2x^2+11x+12=(x+4)(2x+3)}}}.



Note: you can check the answer by expanding {{{(x+4)(2x+3)}}} to get {{{2x^2+11x+12}}} or by graphing the original expression and the answer (the two graphs should be identical).