Diketahui rumus fungsi f (x) = ax+b. Jika f(2) = -2 dan f(-3) = 13maka nilai f(4) adalah

f(2)= -2
f(-3)=13
f(4)=.....?

jawab :
f(2)=-2
f(-3)=13

2a+b=-2
-3a+b=13
________-
5a=-15
a=-3

2a+b=-2
2(-3)+b=-2
-6+b=-2
b=4

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