Question 705107


{{{8w^2-88w+144}}} Start with the given expression.



{{{8(w^2-11w+18)}}} Factor out the GCF {{{8}}}.



Now let's try to factor the inner expression {{{w^2-11w+18}}}



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Looking at the expression {{{w^2-11w+18}}}, we can see that the first coefficient is {{{1}}}, the second coefficient is {{{-11}}}, and the last term is {{{18}}}.



Now multiply the first coefficient {{{1}}} by the last term {{{18}}} to get {{{(1)(18)=18}}}.



Now the question is: what two whole numbers multiply to {{{18}}} (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 {{{18}}} (the previous product).



Factors of {{{18}}}:

1,2,3,6,9,18

-1,-2,-3,-6,-9,-18



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



These factors pair up and multiply to {{{18}}}.

1*18 = 18
2*9 = 18
3*6 = 18
(-1)*(-18) = 18
(-2)*(-9) = 18
(-3)*(-6) = 18


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>18</font></td><td  align="center"><font color=black>1+18=19</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>9</font></td><td  align="center"><font color=black>2+9=11</font></td></tr><tr><td  align="center"><font color=black>3</font></td><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>3+6=9</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>-18</font></td><td  align="center"><font color=black>-1+(-18)=-19</font></td></tr><tr><td  align="center"><font color=red>-2</font></td><td  align="center"><font color=red>-9</font></td><td  align="center"><font color=red>-2+(-9)=-11</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>-6</font></td><td  align="center"><font color=black>-3+(-6)=-9</font></td></tr></table>



From the table, we can see that the two numbers {{{-2}}} and {{{-9}}} add to {{{-11}}} (the middle coefficient).



So the two numbers {{{-2}}} and {{{-9}}} both multiply to {{{18}}} <font size=4><b>and</b></font> add to {{{-11}}}



Now replace the middle term {{{-11w}}} with {{{-2w-9w}}}. Remember, {{{-2}}} and {{{-9}}} add to {{{-11}}}. So this shows us that {{{-2w-9w=-11w}}}.



{{{w^2+highlight(-2w-9w)+18}}} Replace the second term {{{-11w}}} with {{{-2w-9w}}}.



{{{(w^2-2w)+(-9w+18)}}} Group the terms into two pairs.



{{{w(w-2)+(-9w+18)}}} Factor out the GCF {{{w}}} from the first group.



{{{w(w-2)-9(w-2)}}} Factor out {{{9}}} 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.



{{{(w-9)(w-2)}}} Combine like terms. Or factor out the common term {{{w-2}}}



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So {{{8(w^2-11w+18)}}} then factors further to {{{8(w-9)(w-2)}}}



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Answer:



So {{{8w^2-88w+144}}} completely factors to {{{8(w-9)(w-2)}}}.



In other words, {{{8w^2-88w+144=8(w-9)(w-2)}}}.



Note: you can check the answer by expanding {{{8(w-9)(w-2)}}} to get {{{8w^2-88w+144}}} or by graphing the original expression and the answer (the two graphs should be identical).


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Jim


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