The cost of producing x air conditioners is c=g(x)=900+100x. Find a formula for the inverse function g^-1(c). I don't understand inverse functions at all. Please help me.
$\displaystyle c = 900 + 100x$
To get the inverse solve for x
$\displaystyle c - 900 = 100x$
$\displaystyle \frac{c}{100} -9 = x$
Now just swap variables
$\displaystyle c = \frac{x}{100} -9$
There is your inverse
$\displaystyle g^{-1}(x) = \frac{x}{100} -9$