Find f^-1(x)
f(x)=3sqrtx-7 Please help

Question

Find f^-1(x)
f(x)=3sqrtx-7 Please help

hartnn · Answer

let y= 3$\sqrt x$-7
interchange, x and y
x= 3$\sqrt y$-7
now can u fin y in terms of x ?

anonymous · Answer

no I have no clue what I'm doing and really need help

hartnn · Answer

to find inverse function, u find x in terms of f(x)
for convenience, i took it as y
when i interchanged variables, now i need to find y in terms of x, so can u ?

anonymous · Answer

I can't do math for the life of me and can't figure it out

anonymous · Answer

Is it (x+7)^2 this only thing that I can come up with

hartnn · Answer

oh, u get (x+7)^2 = 9y , isn't it ?

anonymous · Answer

I have no idea what the correct answer is, I don't understand where your coming up with the 9y

hartnn · Answer

let me show you
x= 3 $\sqrt y-7$
Adding 7 to both sides
x+7 =3 $\sqrt y$
squaring both sides
(x+7)^2=9y
got this ?

anonymous · Answer

so f^-1(x)=(x+7)^2= 9y ?? Understanding that x+7 ^2 = (x+7) and 3^2 = 9

hartnn · Answer

to get f^-1 x, u need to isolate y
so y= (x+7)^2/9 .....(dividing 9 on both sides)
so that will be your f^-1(x) = (x+7)^2/9
got it ?

anonymous · Answer

Yes I do thanks you

hartnn · Answer

welcome :)