Question

Answer the following:

If f(x) = 3x + a and f(1) = 7 find a and f(4)

Answer 1

f(x) = 3x + a 

∴ f(1) = 3(1) + a = 3 + a

∴ f(1) = 7 gives

3 + a = 7

∴ a = 4

∴ f(x) = 3x + 4

∴ f(4) = 3(4) + 4 = 16.