Diketahui f(x) = ax + b. Jika f(2) = 1 dan f(4) = 7, maka nilai (a - b) adalah...

f(x) = ax+b
f(2) = 2a+b = 1 - - - - > 2(3) +b =1
f(4) = 4a+b = 7 6+b=1
___________ - b= -5
- 2a=-6
a=3
Jadi, (a-b) = 3-(-5) = 8

f(x) = ax + b
f(2) = 1
f(4) = 7

1 = 2a + b
7 = 4a + b
-------------- -
-6 = -2a
a = 3

1 = 2a + b
1 = 2.3 + b
1 = 6 + b
b = -5

a-b = 3-(-5) = 8