Question 303249
First, multiply the first term by the third term, 2*(-18) = -36


You need to find two numbers that multiply to -36, but add up to -9.


List the factors of 36: 36 and 1, 12 and 3, 9 and 4, 6 and 6....


You should notice that 12 and 3 are the only pair that could add up to 9.

Now we will re-write the equation with these factors:

2a^2 -9a - 18
2a^2 - 12a + 3a - 18


Now factor out the 2a from the first pair, and the 3 from the second pair.


2a(a-6) + 3(a-6)


Notice that the (a-6) terms are identical. Now re-arrange, combining the 2a and the 3:

(2a+3)(a-6)


Use F.O.I.L. to check that it is correct. It should equal 2a^2 -9a -18