Diketahui u10=41 u5=21 Berapakah nilai u20 ?

f(x) = ax + b
f(10) = a(10) + b
= 10a + b = 41

f(5) = a(5) + b
= 5a + b = 21

10a + b = 41
5a + b = 21
-----------------(-)
5a = 20
a = 20/5 = 4

4(10) + b = 41
b = 41 - 40
b = 1

f(x) = 4(x) + 1
f(20) = 4(x) + 1
= 4(20) + 1
= 80 + 1
= 81





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