Diketahui f(x) = x – 3, g(x) = 5x + 4 , dan (f o g)(a) = 8 . Nilai a adalah

Diketahui f(x) = x – 3, g(x) = 5x + 4 , dan (f o g)(a) = 8 . Nilai a adalah

Jawaban : 7/5

Perhatikan penjelasan berikut ya.

Ingat kembali pada komposisi fungsi f(x) dan g(x) berlaku:
(fog)(x) = f(g(x))
(gof)(x) = g(f(x))

Diketahui: f(x) = x – 3, g(x) = 5x + 4, dan (fog)(a) = 8

Ditanya : nilai a= … ?

Maka:
(fog)(x) = f(g(x))
(fog)(x) = f(5x + 4)
(fog)(x) = (5x + 4) – 3
(fog)(x) = 5x + 4 – 3
(fog)(x) = 5x + 1

Sehingga:
(fog)(x) = 5x + 1
(fog)(a) = 5(a) + 1
8 = 5a + 1
5a + 1 = 8
5a = 8 – 1
5a = 7
a = 7/5

Jadi, nilai a adalah 7/5.

Semoga membantu.

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