fungsi f dinyatakan dengan rumus f(x)=ax+b. jika f (2)=3 dan f(-3)=13, beapa nilai -a+b?

Kelas 8 Matematika
Bab Fungsi

f(x) = ax + b

f(2) = 2a + b = 3
f(-3) = -3a + b = 13

2a + b = 3
-3a + b = 13
------------------- -
5a = -10
a = -2

2a + b = 3
2 . (-2) + b = 3
b = 3 + 4
b = 7

-a + b =  - (-2) + 7
-a + b = 9

3 = 2a+b. b = 3-2a

13 = -3a+b
= -3a+(3-2a)
= -5a+3
10= -5a
a = -2
b = 3- 2(-2) = 7

-a+b = -(-2)+7 = 9