Question

if f(x)=x+5,then for what value of x does f(4x)=f(x+4)

Answer 1

Substitute in the original equation, and then set them = and solve for x.

Answer 2

Eg.:

f(4x)=4x + 5 (just using 4x in place of x in f(x))

Now do the same thing to find f(4+x).

Set the two expressions = and solve for x.