SOLUTION: Let f(x) = x2 - 8x + 5. Find f(-1)

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Question 886820: Let f(x) = x2 - 8x + 5. Find f(-1)
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
Let's say you want y=f%5E-1%28x%29. Solve for y in y%5E2-8y%2B5=x. You may need to complete the square for y to do it.


y%5E2-8y%2B16-16%2B5=x%2B16, the 16 completes the missing square
%28y-4%29%5E2-16%2B5=x%2B16
%28y-4%29%5E2-11=x%2B16
%28y-4%29%5E2=x%2B16%2B11
%28y-4%29%5E2=x%2B27
y-4=0%2B-+sqrt%28x%2B27%29
highlight%28y=4%2B-+sqrt%28x%2B27%29%29

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!

Let f(x) = x2 - 8x + 5. Find f(-1)


f%28x%29+=+x%5E2+-+8x+%2B+5

f%28-+1%29+=+%28-+1%29%5E2+-+8%28-+1%29+%2B+5

f%28-+1%29+=+1+%2B+8+%2B+5

highlight_green%28highlight_green%28f%28-+1%29+=+14%29%29