Diketahui rumus suatu fungsi f (x) = ax + b, f (3) = 5 dan f (-1) = -3. Nilai f (4) adalah...

f(3) = 3a + b = 5
f(-1)= -a + b = -3
----------------------- -
..........4a = 8
a = 2, masukan pd salahsatu
-2 + b = -3
b = -1
f(x) = 2x - 1