How do I find f-1(x) for f (x) = -2x+5÷8

The answer I got was; f-1 (x)= 8/-2 x + 5/-2

But I'm unsure about my answer and my work, can Anyone help me out with this please! & Thank you

Guest Mar 3, 2015

#1**+10 **

f (x) = -2x+5÷8

Write f(x) as y

y = -2x + (5/8) subtract (5/8) from both sides

y - (5/8) = -2x multiply both sides by -1/2

-(1/2)y + 5/16 = x get a common denominator on the left

[-8y + 5] / 16 = x "exchange" x and y

[-8x + 5] / 16 = y for "y" write f^{-1}(x)

f^{-1}(x) = [-8x + 5]/ 16

Check...putting 0 into the original function leads to 5/8....and putting 5/8 into the inverse leads to 0

CPhill
Mar 3, 2015

#1**+10 **

Best Answer

f (x) = -2x+5÷8

Write f(x) as y

y = -2x + (5/8) subtract (5/8) from both sides

y - (5/8) = -2x multiply both sides by -1/2

-(1/2)y + 5/16 = x get a common denominator on the left

[-8y + 5] / 16 = x "exchange" x and y

[-8x + 5] / 16 = y for "y" write f^{-1}(x)

f^{-1}(x) = [-8x + 5]/ 16

Check...putting 0 into the original function leads to 5/8....and putting 5/8 into the inverse leads to 0

CPhill
Mar 3, 2015