Question 370520


Looking at the expression {{{6x^2-13x+6}}}, we can see that the first coefficient is {{{6}}}, the second coefficient is {{{-13}}}, and the last term is {{{6}}}.



Now multiply the first coefficient {{{6}}} by the last term {{{6}}} to get {{{(6)(6)=36}}}.



Now the question is: what two whole numbers multiply to {{{36}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{-13}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{36}}} (the previous product).



Factors of {{{36}}}:

1,2,3,4,6,9,12,18,36

-1,-2,-3,-4,-6,-9,-12,-18,-36



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



These factors pair up and multiply to {{{36}}}.

1*36 = 36
2*18 = 36
3*12 = 36
4*9 = 36
6*6 = 36
(-1)*(-36) = 36
(-2)*(-18) = 36
(-3)*(-12) = 36
(-4)*(-9) = 36
(-6)*(-6) = 36


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{-13}}}:



<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>36</font></td><td  align="center"><font color=black>1+36=37</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>18</font></td><td  align="center"><font color=black>2+18=20</font></td></tr><tr><td  align="center"><font color=black>3</font></td><td  align="center"><font color=black>12</font></td><td  align="center"><font color=black>3+12=15</font></td></tr><tr><td  align="center"><font color=black>4</font></td><td  align="center"><font color=black>9</font></td><td  align="center"><font color=black>4+9=13</font></td></tr><tr><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>6+6=12</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>-36</font></td><td  align="center"><font color=black>-1+(-36)=-37</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>-18</font></td><td  align="center"><font color=black>-2+(-18)=-20</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>-12</font></td><td  align="center"><font color=black>-3+(-12)=-15</font></td></tr><tr><td  align="center"><font color=red>-4</font></td><td  align="center"><font color=red>-9</font></td><td  align="center"><font color=red>-4+(-9)=-13</font></td></tr><tr><td  align="center"><font color=black>-6</font></td><td  align="center"><font color=black>-6</font></td><td  align="center"><font color=black>-6+(-6)=-12</font></td></tr></table>



From the table, we can see that the two numbers {{{-4}}} and {{{-9}}} add to {{{-13}}} (the middle coefficient).



So the two numbers {{{-4}}} and {{{-9}}} both multiply to {{{36}}} <font size=4><b>and</b></font> add to {{{-13}}}



Now replace the middle term {{{-13x}}} with {{{-4x-9x}}}. Remember, {{{-4}}} and {{{-9}}} add to {{{-13}}}. So this shows us that {{{-4x-9x=-13x}}}.



{{{6x^2+highlight(-4x-9x)+6}}} Replace the second term {{{-13x}}} with {{{-4x-9x}}}.



{{{(6x^2-4x)+(-9x+6)}}} Group the terms into two pairs.



{{{2x(3x-2)+(-9x+6)}}} Factor out the GCF {{{2x}}} from the first group.



{{{2x(3x-2)-3(3x-2)}}} Factor out {{{3}}} 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.



{{{(2x-3)(3x-2)}}} Combine like terms. Or factor out the common term {{{3x-2}}}



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Answer:



So {{{6x^2-13x+6}}} factors to {{{(2x-3)(3x-2)}}}.



In other words, {{{6x^2-13x+6=(2x-3)(3x-2)}}}.



Note: you can check the answer by expanding {{{(2x-3)(3x-2)}}} to get {{{6x^2-13x+6}}} or by graphing the original expression and the answer (the two graphs should be identical).



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Jim