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

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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
+90023
+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
+90023
+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