Question 481981


{{{40k^2-112k+24}}} Start with the given expression.



{{{8(5k^2-14k+3)}}} Factor out the GCF {{{8}}}.



Now let's try to factor the inner expression {{{5k^2-14k+3}}}



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Looking at the expression {{{5k^2-14k+3}}}, we can see that the first coefficient is {{{5}}}, the second coefficient is {{{-14}}}, and the last term is {{{3}}}.



Now multiply the first coefficient {{{5}}} by the last term {{{3}}} to get {{{(5)(3)=15}}}.



Now the question is: what two whole numbers multiply to {{{15}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{-14}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{15}}} (the previous product).



Factors of {{{15}}}:

1,3,5,15

-1,-3,-5,-15



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



These factors pair up and multiply to {{{15}}}.

1*15 = 15
3*5 = 15
(-1)*(-15) = 15
(-3)*(-5) = 15


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{-14}}}:



<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>15</font></td><td  align="center"><font color=black>1+15=16</font></td></tr><tr><td  align="center"><font color=black>3</font></td><td  align="center"><font color=black>5</font></td><td  align="center"><font color=black>3+5=8</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>-15</font></td><td  align="center"><font color=black>-1+(-15)=-16</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>-5</font></td><td  align="center"><font color=black>-3+(-5)=-8</font></td></tr></table>



From the table, we can see that there are no pairs of numbers which add to {{{-14}}}. So {{{5k^2-14k+3}}} cannot be factored.



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Answer:



So {{{40k^2-112k+24}}} simply factors to {{{8(5k^2-14k+3)}}}



In other words, {{{40k^2-112k+24=8(5k^2-14k+3)}}}.