Question

If f(x) = 3x + 1, then f(a + h) - f(a) =

Answer 1

F(a+h) = 3(a+h) + 1 = 3a + 3h + 1

f(a) = 3a + 1

f(a+h) - f(a) = 3a + 3h + 1 - 3a - 1 = 3h

Answer: 3h

Answer 2

Replace x with a+h and a

f(a+h)-f(a)=3(a+h)+1-(3a+1)=
3a+3h+1-3a-1=
3h

result is 3h