Question

Let f(x) = x2 – 81. Find f–1(x).

Answer 1

f(x)=x^2-81

let's define f(x)=y

Answer 2

y=x^2-81

Answer 3

now switch variable

Answer 4

x=y^2-81

solve for y

Answer 5

I'm not sure how too

Answer 6

start by addng 81 to both sides

Answer 7

x + 81= y2

Answer 8

??

Answer 9

good

Answer 10

y^2=x+81

now take square root of both sides

Answer 11

+- x + 81?

Answer 12

I think you meant
\[\pm\sqrt{x+81}\]?

Answer 13

Yes

Answer 14

yep, that's it; that's f^-1(x)

Answer 15

Thanks so much!

Answer 16

you are welcome