Question 243717


Looking at the expression {{{x^2+24x+144}}}, we can see that the first coefficient is {{{1}}}, the second coefficient is {{{24}}}, and the last term is {{{144}}}.



Now multiply the first coefficient {{{1}}} by the last term {{{144}}} to get {{{(1)(144)=144}}}.



Now the question is: what two whole numbers multiply to {{{144}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{24}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{144}}} (the previous product).



Factors of {{{144}}}:

1,2,3,4,6,8,9,12,16,18,24,36,48,72,144

-1,-2,-3,-4,-6,-8,-9,-12,-16,-18,-24,-36,-48,-72,-144



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



These factors pair up and multiply to {{{144}}}.

1*144 = 144
2*72 = 144
3*48 = 144
4*36 = 144
6*24 = 144
8*18 = 144
9*16 = 144
12*12 = 144
(-1)*(-144) = 144
(-2)*(-72) = 144
(-3)*(-48) = 144
(-4)*(-36) = 144
(-6)*(-24) = 144
(-8)*(-18) = 144
(-9)*(-16) = 144
(-12)*(-12) = 144


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{24}}}:



<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>144</font></td><td  align="center"><font color=black>1+144=145</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>72</font></td><td  align="center"><font color=black>2+72=74</font></td></tr><tr><td  align="center"><font color=black>3</font></td><td  align="center"><font color=black>48</font></td><td  align="center"><font color=black>3+48=51</font></td></tr><tr><td  align="center"><font color=black>4</font></td><td  align="center"><font color=black>36</font></td><td  align="center"><font color=black>4+36=40</font></td></tr><tr><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>24</font></td><td  align="center"><font color=black>6+24=30</font></td></tr><tr><td  align="center"><font color=black>8</font></td><td  align="center"><font color=black>18</font></td><td  align="center"><font color=black>8+18=26</font></td></tr><tr><td  align="center"><font color=black>9</font></td><td  align="center"><font color=black>16</font></td><td  align="center"><font color=black>9+16=25</font></td></tr><tr><td  align="center"><font color=red>12</font></td><td  align="center"><font color=red>12</font></td><td  align="center"><font color=red>12+12=24</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>-144</font></td><td  align="center"><font color=black>-1+(-144)=-145</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>-72</font></td><td  align="center"><font color=black>-2+(-72)=-74</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>-48</font></td><td  align="center"><font color=black>-3+(-48)=-51</font></td></tr><tr><td  align="center"><font color=black>-4</font></td><td  align="center"><font color=black>-36</font></td><td  align="center"><font color=black>-4+(-36)=-40</font></td></tr><tr><td  align="center"><font color=black>-6</font></td><td  align="center"><font color=black>-24</font></td><td  align="center"><font color=black>-6+(-24)=-30</font></td></tr><tr><td  align="center"><font color=black>-8</font></td><td  align="center"><font color=black>-18</font></td><td  align="center"><font color=black>-8+(-18)=-26</font></td></tr><tr><td  align="center"><font color=black>-9</font></td><td  align="center"><font color=black>-16</font></td><td  align="center"><font color=black>-9+(-16)=-25</font></td></tr><tr><td  align="center"><font color=black>-12</font></td><td  align="center"><font color=black>-12</font></td><td  align="center"><font color=black>-12+(-12)=-24</font></td></tr></table>



From the table, we can see that the two numbers {{{12}}} and {{{12}}} add to {{{24}}} (the middle coefficient).



So the two numbers {{{12}}} and {{{12}}} both multiply to {{{144}}} <font size=4><b>and</b></font> add to {{{24}}}



Now replace the middle term {{{24x}}} with {{{12x+12x}}}. Remember, {{{12}}} and {{{12}}} add to {{{24}}}. So this shows us that {{{12x+12x=24x}}}.



{{{x^2+highlight(12x+12x)+144}}} Replace the second term {{{24x}}} with {{{12x+12x}}}.



{{{(x^2+12x)+(12x+144)}}} Group the terms into two pairs.



{{{x(x+12)+(12x+144)}}} Factor out the GCF {{{x}}} from the first group.



{{{x(x+12)+12(x+12)}}} Factor out {{{12}}} 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+12)(x+12)}}} Combine like terms. Or factor out the common term {{{x+12}}}



{{{(x+12)^2}}} Condense the terms.



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Answer:



So {{{x^2+24x+144}}} factors to {{{(x+12)^2}}}.



In other words, {{{x^2+24x+144=(x+12)^2}}}.



Note: you can check the answer by expanding {{{(x+12)^2}}} to get {{{x^2+24x+144}}} or by graphing the original expression and the answer (the two graphs should be identical).