Question

if f(x)= 5x+6/7x+9 then f-1(x)

Answer 1

Given: f(x)= 5x+6 / 7x+9

To find: f^-1(x) = ?

Solution:

• Now we have given f(x) = 5x+6 / 7x+9

• Let f(x) = y, then:

                 y = 5x+6 / 7x+9

                 7xy + 9y = 5x + 6

                 7xy - 5x = 6 - 9y

                 x(7y - 5) = 6 - 9y

                 x = 6 - 9y / 7y - 5

• Now as we have written above that:

                 y = f(x), so x = f^-1(y)

                 f^-1(y) = 6 - 9y / 7y - 5

• Similarly:

                 f^-1(x) = 6 - 9x / 7x - 5

Answer:

             So the f^-1(x) is 6 - 9x / 7x - 5.