Question 191799


Looking at the expression {{{x^2+22x+57}}}, we can see that the first coefficient is {{{1}}}, the second coefficient is {{{22}}}, and the last term is {{{57}}}.



Now multiply the first coefficient {{{1}}} by the last term {{{57}}} to get {{{(1)(57)=57}}}.



Now the question is: what two whole numbers multiply to {{{57}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{22}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{57}}} (the previous product).



Factors of {{{57}}}:

1,3,19,57

-1,-3,-19,-57



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



These factors pair up and multiply to {{{57}}}.

1*57
3*19
(-1)*(-57)
(-3)*(-19)


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{22}}}:



<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>57</font></td><td  align="center"><font color=black>1+57=58</font></td></tr><tr><td  align="center"><font color=red>3</font></td><td  align="center"><font color=red>19</font></td><td  align="center"><font color=red>3+19=22</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>-57</font></td><td  align="center"><font color=black>-1+(-57)=-58</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>-19</font></td><td  align="center"><font color=black>-3+(-19)=-22</font></td></tr></table>



From the table, we can see that the two numbers {{{3}}} and {{{19}}} add to {{{22}}} (the middle coefficient).



So the two numbers {{{3}}} and {{{19}}} both multiply to {{{57}}} <font size=4><b>and</b></font> add to {{{22}}}



Now replace the middle term {{{22x}}} with {{{3x+19x}}}. Remember, {{{3}}} and {{{19}}} add to {{{22}}}. So this shows us that {{{3x+19x=22x}}}.



{{{x^2+highlight(3x+19x)+57}}} Replace the second term {{{22x}}} with {{{3x+19x}}}.



{{{(x^2+3x)+(19x+57)}}} Group the terms into two pairs.



{{{x(x+3)+(19x+57)}}} Factor out the GCF {{{x}}} from the first group.



{{{x(x+3)+19(x+3)}}} Factor out {{{19}}} 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+19)(x+3)}}} Combine like terms. Or factor out the common term {{{x+3}}}


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Answer:



So {{{x^2+22x+57}}} factors to {{{(x+19)(x+3)}}}.



Note: you can check the answer by FOILing {{{(x+19)(x+3)}}} to get {{{x^2+22x+57}}} or by graphing the original expression and the answer (the two graphs should be identical).