Question

Diketahui rumus fungsi f(x) = ax+b, jika f(3) = 18dan f(7) = 38 ,maka nilai f(24) adalah
a.54
b.56
c.123
d.166

Answer 1

F (x) = ax + b
f (3) = a(3) + b
= 3a + b
f (7) = a(7) + b
= 7a + b

7a + b = 38
3a + b = 18-
4a = 20
a = 20 / 4
a = 5

3a + b = 18
3(5) + b = 18
15 + b = 18
b = 18 - 15
b = 3

f (x) = ax + b
f (x) = 5x + 3

f(24) = 5(24) + 3
= 120 + 3
= 123

Answer 2

F(x)=ax+b
f(3)=3a+b
18=3a+b.....(1)
f(7)=7a+b
38=7a+b.....(2)
kemudian eliminasi persamaan 1 dan 2
3a+b=18
7a+b=38
-4a=-20
a=5
subtitusikan a ke salah satu persamaan
3(5)+b=18
15+b=18
b=3
sekarang subtitusikan x, a, dan b ke persamaan f(x)
f(24)=5(24)+3
      =123