Question 576488


Looking at the expression {{{6s^2-s-5}}}, we can see that the first coefficient is {{{6}}}, the second coefficient is {{{-1}}}, and the last term is {{{-5}}}.



Now multiply the first coefficient {{{6}}} by the last term {{{-5}}} to get {{{(6)(-5)=-30}}}.



Now the question is: what two whole numbers multiply to {{{-30}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{-1}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{-30}}} (the previous product).



Factors of {{{-30}}}:

1,2,3,5,6,10,15,30

-1,-2,-3,-5,-6,-10,-15,-30



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



These factors pair up and multiply to {{{-30}}}.

1*(-30) = -30
2*(-15) = -30
3*(-10) = -30
5*(-6) = -30
(-1)*(30) = -30
(-2)*(15) = -30
(-3)*(10) = -30
(-5)*(6) = -30


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{-1}}}:



<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>-30</font></td><td  align="center"><font color=black>1+(-30)=-29</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>-15</font></td><td  align="center"><font color=black>2+(-15)=-13</font></td></tr><tr><td  align="center"><font color=black>3</font></td><td  align="center"><font color=black>-10</font></td><td  align="center"><font color=black>3+(-10)=-7</font></td></tr><tr><td  align="center"><font color=red>5</font></td><td  align="center"><font color=red>-6</font></td><td  align="center"><font color=red>5+(-6)=-1</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>30</font></td><td  align="center"><font color=black>-1+30=29</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>15</font></td><td  align="center"><font color=black>-2+15=13</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>10</font></td><td  align="center"><font color=black>-3+10=7</font></td></tr><tr><td  align="center"><font color=black>-5</font></td><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>-5+6=1</font></td></tr></table>



From the table, we can see that the two numbers {{{5}}} and {{{-6}}} add to {{{-1}}} (the middle coefficient).



So the two numbers {{{5}}} and {{{-6}}} both multiply to {{{-30}}} <font size=4><b>and</b></font> add to {{{-1}}}



Now replace the middle term {{{-1s}}} with {{{5s-6s}}}. Remember, {{{5}}} and {{{-6}}} add to {{{-1}}}. So this shows us that {{{5s-6s=-1s}}}.



{{{6s^2+highlight(5s-6s)-5}}} Replace the second term {{{-1s}}} with {{{5s-6s}}}.



{{{(6s^2+5s)+(-6s-5)}}} Group the terms into two pairs.



{{{s(6s+5)+(-6s-5)}}} Factor out the GCF {{{s}}} from the first group.



{{{s(6s+5)-1(6s+5)}}} Factor out {{{1}}} 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.



{{{(s-1)(6s+5)}}} Combine like terms. Or factor out the common term {{{6s+5}}}



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Answer:



So {{{6s^2-s-5}}} factors to {{{(s-1)(6s+5)}}}.



In other words, {{{6s^2-s-5=(s-1)(6s+5)}}}.



Note: you can check the answer by expanding {{{(s-1)(6s+5)}}} to get {{{6s^2-s-5}}} or by graphing the original expression and the answer (the two graphs should be identical).