Question

Function f is defined by the equationf(x)=5x−9. Find the value of c so that f(c)=21 is true.

Answer 1

c=6

Explanation:

f(x)=5x-9

c=x

f(x)=f(c)=21

5x-9=21

5x=21+9

5x=30

x=6

c=6