suatu fungsi dirumuskan f (x) = ax+b jika f (-2) = 14 dqn f (3) = -1 maka nilai f (4) adalah

f(x) = ax + b

f(-2) = -2a + b
14 = -2a + b

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

eliminasi b
-2a + b = 14
3a + b = -1
________-
-5a = 15
a = -3

substitusi a = -3 ke persamaan 3a + b = -1
3(-3) + b = -1
-9 + b = -1
b = -1 + 9
b = 8

maka fungsinya f(x) = -3x + 8

f(4) = -3(4) + 8 = -12 + 8 = -4