SOLUTION: f(x)= x^2-4x find f^-1(x)

Question 685731: f(x)= x^2-4x
find f^-1(x)
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
f(x)= x^2-4x
find f^-1(x)
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1st: Interchange x and y to get:
x = y^2-4y
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2nd: Solve for "y":
y^2-4y-x = 0
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y = [4 +- sqrt(16-4*-x)]/2
--
y = [4 +- sqrt(16+4x)]/2
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f^-1(x) = [4 + sqrt(16+4x)]/2 or f^-1(x) = [4 - sqrt(16+4x)]/2
====================
Cheers,
Stan H.
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