Question

f(x)=2x^2-x-1. If f(x)=-1, what is x?

Answer 1

f(x)=2x^2-x-1

-1=2x^2-x-1 ... replace f(x) with -1 (since f(x) = -1)

-1+1=2x^2-x-1+1

0 = 2x^2 - x

2x^2 - x = 0

I'll let you finish

Answer 2

That's what I have right now. I don't know what to do next. I factored out an x so I have\[x(2x-1)=0\]

Answer 3

remember that if A*B = 0, then either A = 0 or B = 0 (or both could equal zero)

Answer 4

so this means that if

x*(2x-1) = 0

then

x = 0 or 2x - 1 = 0

Answer 5

I keep forgetting basic stuff... Thanks.

Answer 6

yw