Answer
Let f(x) = ax + b
Then
f(x + 1) = a(x + 1) + b
= ax + a + b
Hence, a = 3, and a + b = 5, b = 2
f(-2) = 3(-2) + 2
= -6 + 2
= - 4
f(2x) = 3(2x ) + 2
= 6x + 2
