Question

A formula for a function y=f(x) is f(x)=x^2-10x,xless than or equal 5. Find f^-1(x) and indentify the domain and range of f^-1(x). Is f(f^-1(x)))=f^-1(f(x))=x?

Answer 1

f(x) =x² - 10x, f⁻¹(x) =?

1st find the missing square of x²-10x, ==> (x-5)² - 25

y= (x-5)² - 25; replace x by y and v0ce versa: x= (y-5)² -25
or
(y-5)² = x+25
y-5 = √(x+25) and y = √(x+25) -5

Domain = {x∈R: X>= 25} AND Range ={y∈R: y>= 5}