x=3 f(x)=8. x=4 f(x)=11

misal f(x) = ax+b
f(3) = 8
3a+b = 8......(1)

f(4) = 11
4a+b = 11......(2)

3a+b=8
b=8-3a

4a+b=11
4a+8-3a=11
4a-3a=11-8
a=3

3a+b=8
3.3+b=8
9+b=8
b=8-9
b=-1

f(x)=ax+b
f(x)=3x-1

semoga membantu:)