Question 585510


Looking at the expression {{{x^2-16x+60}}}, we can see that the first coefficient is {{{1}}}, the second coefficient is {{{-16}}}, and the last term is {{{60}}}.



Now multiply the first coefficient {{{1}}} by the last term {{{60}}} to get {{{(1)(60)=60}}}.



Now the question is: what two whole numbers multiply to {{{60}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{-16}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{60}}} (the previous product).



Factors of {{{60}}}:

1,2,3,4,5,6,10,12,15,20,30,60

-1,-2,-3,-4,-5,-6,-10,-12,-15,-20,-30,-60



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



These factors pair up and multiply to {{{60}}}.

1*60 = 60
2*30 = 60
3*20 = 60
4*15 = 60
5*12 = 60
6*10 = 60
(-1)*(-60) = 60
(-2)*(-30) = 60
(-3)*(-20) = 60
(-4)*(-15) = 60
(-5)*(-12) = 60
(-6)*(-10) = 60


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{-16}}}:



<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>60</font></td><td  align="center"><font color=black>1+60=61</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>30</font></td><td  align="center"><font color=black>2+30=32</font></td></tr><tr><td  align="center"><font color=black>3</font></td><td  align="center"><font color=black>20</font></td><td  align="center"><font color=black>3+20=23</font></td></tr><tr><td  align="center"><font color=black>4</font></td><td  align="center"><font color=black>15</font></td><td  align="center"><font color=black>4+15=19</font></td></tr><tr><td  align="center"><font color=black>5</font></td><td  align="center"><font color=black>12</font></td><td  align="center"><font color=black>5+12=17</font></td></tr><tr><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>10</font></td><td  align="center"><font color=black>6+10=16</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>-60</font></td><td  align="center"><font color=black>-1+(-60)=-61</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>-30</font></td><td  align="center"><font color=black>-2+(-30)=-32</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>-20</font></td><td  align="center"><font color=black>-3+(-20)=-23</font></td></tr><tr><td  align="center"><font color=black>-4</font></td><td  align="center"><font color=black>-15</font></td><td  align="center"><font color=black>-4+(-15)=-19</font></td></tr><tr><td  align="center"><font color=black>-5</font></td><td  align="center"><font color=black>-12</font></td><td  align="center"><font color=black>-5+(-12)=-17</font></td></tr><tr><td  align="center"><font color=red>-6</font></td><td  align="center"><font color=red>-10</font></td><td  align="center"><font color=red>-6+(-10)=-16</font></td></tr></table>



From the table, we can see that the two numbers {{{-6}}} and {{{-10}}} add to {{{-16}}} (the middle coefficient).



So the two numbers {{{-6}}} and {{{-10}}} both multiply to {{{60}}} <font size=4><b>and</b></font> add to {{{-16}}}



Now replace the middle term {{{-16x}}} with {{{-6x-10x}}}. Remember, {{{-6}}} and {{{-10}}} add to {{{-16}}}. So this shows us that {{{-6x-10x=-16x}}}.



{{{x^2+highlight(-6x-10x)+60}}} Replace the second term {{{-16x}}} with {{{-6x-10x}}}.



{{{(x^2-6x)+(-10x+60)}}} Group the terms into two pairs.



{{{x(x-6)+(-10x+60)}}} Factor out the GCF {{{x}}} from the first group.



{{{x(x-6)-10(x-6)}}} Factor out {{{10}}} 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-10)(x-6)}}} Combine like terms. Or factor out the common term {{{x-6}}}



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Answer:



So {{{x^2-16x+60}}} factors to {{{(x-10)(x-6)}}}.



In other words, {{{x^2-16x+60=(x-10)(x-6)}}}.



Note: you can check the answer by expanding {{{(x-10)(x-6)}}} to get {{{x^2-16x+60}}} or by graphing the original expression and the answer (the two graphs should be identical).


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