if f(x)=-5x-11 then f^-1(x)= ?
inverse functions confuse me please help

Question

if f(x)=-5x-11 then f^-1(x)= ?
inverse functions confuse me please help

anonymous · Answer

can you solve 
$$-5x-11=7$$?

anonymous · Answer

for example i mean
it takes two steps only

anonymous · Answer

$$x=-\frac{ -18 }{ ?5}$$

anonymous · Answer

well $$\frac{18}{5}$$yes
how did you do it?

anonymous · Answer

I did the work and checked it with a calculator

anonymous · Answer

"the work" being what ?

anonymous · Answer

but is that all there is to it?

anonymous · Answer

two steps right? what were those two steps?

anonymous · Answer

switch x and y, solve for y and x, and substitute f^-1 for y

anonymous · Answer

my school teaches it in three steps

anonymous · Answer

but that isn't the answer they want

anonymous · Answer

ok all i was trying to point out is that if you can solve 
$$-5x-11=7$$ that means if you know the output 7, you know the input $\frac{18}{5}$ the two steps where 
a) add 11
b) divide by $-5$ 
that is what the inverse does

anonymous · Answer

if you cannot do it in your head (which you can) solve 
$$-5y-11=x$$ for $y$ same two steps 
a) add 11$$-5y=x+11$$divide by $-5$ 
$$y=\frac{x+11}{-5}$$

anonymous · Answer

or if you want to pull out the minus sign, write 
$$f^{-1}(x)=-\frac{x+11}{5}$$