Diketahui suatu fungsi f(x) = ax + b memiliki nilai f(-1) = 1 dan f(2) = 13. nilai f(4) adalah

f(x) = ax + b
f(-1) = a(-1) + b = 1
f(2) = a(2) + b = 13

-a + b = 1
2a+ b = 13
——————— -
-3a = -12
a = 4

lalu susbstitusikan ke salah satu fungsi disoal
2(4) + b = 13
8 + b = 13
b = 13 - 8
b = 5

f (4) = 4(4) + 5
16 + 5 = 21

f(x) = ax + b
f(-1) = -1a + b = 1
f(2) = 2a + b = 13

-1a + b = 1
2a + b = 13
----------------- -
-3a = -12
a = 4

2a + b = 13
2 . 4 + b = 13
8 + b = 13
b = 5

f(x) = ax + b
f(x) = 4x + 5
f(4) = 4 . 4 + 5
= 16 + 5
= 21