suatu fungsi dirumuskan f(x)=ax +b. jika f(2)= -2 dan f(-3)=13, maka nilai f(4) adalah...

f(x)=ax +b
f(2)=a.2 +b = 2a + b = -2
f(-3)=a. (-3) +b = -3a + b = 13
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2a - ( -3a ) = -2 - 13
5a = -15
a = -3

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

f(4) = -3. 4 + 4 = -12 + 4 = -8