tolong dong di jawab nomor 21-23 pakai caranya ya...... butuh banget....

21.) (B) 1 dan 3
22.)
f(x) = ax + b

*f(2) = -2
a x 2 + b = -2
2a + b = -2

*f(-3) = 13
ax (-3) + b = 13
-3a + b = 13

cara eliminasi:
2a + b = -2
-3a + b = 13
------------------- -
5a = 15
a = 3

cara subsitusi:
2a + b = -2
2 x 3 + b = -2
6 + b = -2
b = (-2) - 6
b = -8

F(4) = ax + b
= 3 x 4 + (-8)
= 12 + (-8)
= 4