Question 112031


Looking at {{{6h^2+17hk+10k^2}}} we can see that the first term is {{{6h^2}}} and the last term is {{{10k^2}}} where the coefficients are 6 and 10 respectively.


Now multiply the first coefficient 6 and the last coefficient 10 to get 60. Now what two numbers multiply to 60 and add to the  middle coefficient 17? Let's list all of the factors of 60:




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 ...List the negative factors as well. This will allow us to find all possible combinations


These factors pair up and multiply to 60

1*60

2*30

3*20

4*15

5*12

6*10

(-1)*(-60)

(-2)*(-30)

(-3)*(-20)

(-4)*(-15)

(-5)*(-12)

(-6)*(-10)


note: remember two negative numbers multiplied together make a positive number



Now which of these pairs add to 17? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to 17


<table border="1"><th>First Number</th><th>Second Number</th><th>Sum</th><tr><td align="center">1</td><td align="center">60</td><td>1+60=61</td></tr><tr><td align="center">2</td><td align="center">30</td><td>2+30=32</td></tr><tr><td align="center">3</td><td align="center">20</td><td>3+20=23</td></tr><tr><td align="center">4</td><td align="center">15</td><td>4+15=19</td></tr><tr><td align="center">5</td><td align="center">12</td><td>5+12=17</td></tr><tr><td align="center">6</td><td align="center">10</td><td>6+10=16</td></tr><tr><td align="center">-1</td><td align="center">-60</td><td>-1+(-60)=-61</td></tr><tr><td align="center">-2</td><td align="center">-30</td><td>-2+(-30)=-32</td></tr><tr><td align="center">-3</td><td align="center">-20</td><td>-3+(-20)=-23</td></tr><tr><td align="center">-4</td><td align="center">-15</td><td>-4+(-15)=-19</td></tr><tr><td align="center">-5</td><td align="center">-12</td><td>-5+(-12)=-17</td></tr><tr><td align="center">-6</td><td align="center">-10</td><td>-6+(-10)=-16</td></tr></table>



From this list we can see that 5 and 12 add up to 17 and multiply to 60



Now looking at the expression {{{6h^2+17hk+10k^2}}}, replace {{{17hk}}} with {{{5hk+12hk}}} (notice {{{5hk+12hk}}} adds up to {{{17hk}}}. So it is equivalent to {{{17hk}}})


{{{6h^2+highlight(5hk+12hk)+10k^2}}}



Now let's factor {{{6h^2+5hk+12hk+10k^2}}} by grouping:



{{{(6h^2+5hk)+(12hk+10k^2)}}} Group like terms



{{{h(6h+5k)+2k(6h+5k)}}} Factor out the GCF of {{{h}}} out of the first group. Factor out the GCF of {{{2k}}} out of the second group



{{{(h+2k)(6h+5k)}}} Since we have a common term of {{{6h+5k}}}, we can combine like terms


So {{{6h^2+5hk+12hk+10k^2}}} factors to {{{(h+2k)(6h+5k)}}}



So this also means that {{{6h^2+17hk+10k^2}}} factors to {{{(h+2k)(6h+5k)}}} (since {{{6h^2+17hk+10k^2}}} is equivalent to {{{6h^2+5hk+12hk+10k^2}}})