For all values of x, f(x)=3x+k, where k is a constant Given that ff(3) = 7, find the value of k? PLEASE HELP

1 Answer
Nov 6, 2017

Not sure if you made a typo here...
if meant F(3) = 7 , then F(3) = 3*3+k = 7 so k equals -2..

Explanation:

If however it meant ff(3) = f(f(3)), then:
f(3) = f(3*3 + k),
=>f(f(3)) = 3(3x+k) + k
=> f(f(3)) = 9x + 4k = 7
x=3, therefore 27+4k = 7
=> 20 + 4k = 0
=> k = -5

hope this helps....???