Question 871368: I need help to factor this trinomial -x^2+7x+18 please explain step by step so I can do it myself :) Found 2 solutions by rothauserc, mananth:Answer by rothauserc(4718) (Show Source):
You can put this solution on YOUR website! start by finding the prime factors of 18 which are 3*3*2
we want to factor -x^2 + 7x + 18
we have (-x + ) times (x + )
looking at the prime factors, we want to get a 7, note that 9 times 2 results in the 7, therefore
-x^2 + 7x + 18 = (-x + 9) times (x + 2)
You can put this solution on YOUR website!
Multiply the first term and the third term
-18x^2
Split the middle term into two parts such that when you add the parts you get 7x and when you multiply them you get -18x^2
In this case the break up is 9 and- 2
9x-2x=7x
9x*-2x = -18x^2
Re write the trinomial
factorize
-x(x-9)-2(x-9)
(x-9)(-x-2)
