Question 853839: Factor Each Trinomial : -4x^2+11x+20
I'm confused on this one, help me please show all work! Thanks.
Found 2 solutions by rothauserc, LinnW:
Answer by rothauserc(4718)   (Show Source):
You can put this solution on YOUR website! we are given -4x^2+11x+20 to factor
first write down all factors of 20
5,2,2,20,1
try the following
4x +5
-x +4
we see that we get -4x^2+11x+20
therefore
(4x+5)(-x+4) are factors of -4x^2+11x+20
Answer by LinnW(1048)  (Show Source):
You can put this solution on YOUR website! -4x^2+11x+20
A good way is to start by factoring out -1
-1(4x^2-11x-20)
Now factor by grouping 4x^2-11x-20
We want two numbers multiplied to get (4)(-20) = -80
where the two numbers added give us -11
Possible factors
1,80
2,40
4,20
5,16 This is the pair we want since 16-5 = 11
The actual pair will be 5,-16
4x^2 -16x +5x -20
4x(x - 4) +5(x - 4)
(4x + 5)(x - 4)
Now put the -1 back in
(-1)(4x + 5)(x - 4)
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