Question 670772


{{{t^3+10t^2-24t}}} Start with the given expression.



{{{t(t^2+10t-24)}}} Factor out the GCF {{{t}}}.



Now let's try to factor the inner expression {{{t^2+10t-24}}}



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Looking at the expression {{{t^2+10t-24}}}, we can see that the first coefficient is {{{1}}}, the second coefficient is {{{10}}}, and the last term is {{{-24}}}.



Now multiply the first coefficient {{{1}}} by the last term {{{-24}}} to get {{{(1)(-24)=-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 {{{10}}}?



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 {{{10}}}:



<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)=-23</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)=-10</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)=-5</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)=-2</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=23</font></td></tr><tr><td  align="center"><font color=red>-2</font></td><td  align="center"><font color=red>12</font></td><td  align="center"><font color=red>-2+12=10</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=5</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=2</font></td></tr></table>



From the table, we can see that the two numbers {{{-2}}} and {{{12}}} add to {{{10}}} (the middle coefficient).



So the two numbers {{{-2}}} and {{{12}}} both multiply to {{{-24}}} <font size=4><b>and</b></font> add to {{{10}}}



Now replace the middle term {{{10t}}} with {{{-2t+12t}}}. Remember, {{{-2}}} and {{{12}}} add to {{{10}}}. So this shows us that {{{-2t+12t=10t}}}.



{{{t^2+highlight(-2t+12t)-24}}} Replace the second term {{{10t}}} with {{{-2t+12t}}}.



{{{(t^2-2t)+(12t-24)}}} Group the terms into two pairs.



{{{t(t-2)+(12t-24)}}} Factor out the GCF {{{t}}} from the first group.



{{{t(t-2)+12(t-2)}}} 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.



{{{(t+12)(t-2)}}} Combine like terms. Or factor out the common term {{{t-2}}}



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So {{{t(t^2+10t-24)}}} then factors further to {{{t(t+12)(t-2)}}}



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Answer:



So {{{t^3+10t^2-24t}}} completely factors to {{{t(t+12)(t-2)}}}.



In other words, {{{t^3+10t^2-24t=t(t+12)(t-2)}}}.



Note: you can check the answer by expanding {{{t(t+12)(t-2)}}} to get {{{t^3+10t^2-24t}}} or by graphing the original expression and the answer (the two graphs should be identical).