If f(x) = (3x-2) / x-5 x>6, find a.) ff(8) b.) the range of f(x) c.) f^-1(x) and state its range.

Firstly, ff(8) is the same as f(f(8)) so f(8) needs to be found first. Subbing in x=8 f(8)=22/3, so f(22/3) is required, Setting x=22/3 f(22/3)= 20/(22/3 - 5) = 60/7. so ff(8)=60/7.Next, as x tends to infinity f(x) tends to 3 at x=6 f(x) = 16. The function never reaches either limit however so 3<f(x)<16.Finally for c.), set y=f(x). The inverse function is a reflection of the original function in f(x), so rearrange y = (3x-2)/x-5 to get x as a function of y. Multiplying both sides by x-5, yx-5y = 3x-2 next group all terms with x to get 3x-yx=2-5y. x(3-y) = 2-5y, so x = (2-5y)/(3-y). Now swap the x and y's, which is the equivalent or the reflection in the line y=x. y = (2-5x)/(3-x) so f^-1(x) = 2-5x/3-x. The range of the inverse of a function is the domain of the original function, so f^-1(x)>6.

Answered by Euan F. Maths tutor

4199 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

a) show that (cosx)^2=8(sinx)^2-6sinx can be written as (3sinx-1)^2=2 b)Solve (cosx)^2=8(sinx)^2-6sinx


Mechanics (M1): Particle moving on a straight line with constant acceleration (Relationships of the 5 Key Formulae)


Find the derivative of f(x)=x^2*e^x+x


Simplify √32 + √18 giving your answer in the form of a√2.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences