What is the inverse of the function y=2x+5?

1 Answer
Jan 2, 2016

If f(x)=2x+5
f(x)1=x52

Explanation:

This method works, but I'm not sure how sound it is mathematically.

Let f(x)=y
so y=2x+5
then rearrange for x
so x=y52
Now swap the subject for f(x)1 and the y for x.
f(x)1=x52

You can check the answer by substituting in a value for x, example x=3

f(3)=6+5=11
Then put the answer of that into the inverse equation, and you should receive the first number you put in.

f(11)1=1152=62=3