SOLUTION: Function: f(x)= 2x^2-x-1 If f(x)= =1, what is x?

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Question 712491: Function: f(x)= 2x^2-x-1
If f(x)= =1, what is x?

Found 2 solutions by algebrahouse.com, MathLover1:
Answer by algebrahouse.com(1659) About Me  (Show Source):
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
f%28x%29=+2x%5E2-x-1
If f%28x%29=1,then
1=+2x%5E2-x-1
or
2x%5E2-x-1=1
2x%5E2-x-1-1=0
2x%5E2-x-2=0...use quadratic formula to solve for x

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x+=+%28-%28-1%29+%2B-+sqrt%28+%28-1%29%5E2-4%2A2%2A%28-2%29+%29%29%2F%282%2A2%29+
x+=+%281+%2B-+sqrt%28+1%2B16+%29%29%2F4+
x+=+%281+%2B-+sqrt%28+17+%29%29%2F4+
x+=+%281+%2B-+4.12%29%2F4+
solutions:
x+=+%281+%2B4.12%29%2F4+
x+=+5.12%2F4+
x+=+1.28+
or
x+=+%281+-4.12%29%2F4+
x+=+-3.12%2F4+
x+=-0.78+