Question

Let f(x) = 4x − 3. If f(a) = 9 and f(b) = 5, then what is f(a + b) ?

Answer 1

F(x) = 4x - 3

f(a) = 4a-3

9 = 4a-3

4a = 12

a = 12 / 4

a = 3

_____________________

f(b) = 4b-3

5+3 = 4b

8 = 4b

b = 8 / 4

b = 2

___________________

f(a+b) = 4(a+b) - 3

f(a+b) = 4(3+2) - 3

f(a+b) = 4(5) - 3

f(a+b) = 20 - 3

f(a+b) = 17