jawab no4 ya jangan ngasal

f(x) = ax + b
f(1) = a + b = 4
f(-2) = - 2a + b = - 5
-----------------------------(-)
3a = 9
a = 3
a + b = 4
3 + b = 4
b = 4 - 3
b = 1

rumus fungsinya adalah :
f(x) = 3x + 1