g(x)=3x-2 & (fog)(x)=9x^2-6x+4. Nilai f(4)

langsung aja y

(fog)(x) = f{g(x)}

9x² - 6x + 4 = f(3x-2)

misal :
f(3x-2) = a
f(3x) = a + 2
f(x) = (a+2) / 3

soal menjadi
f(x) = 9(a+2 / 3)² - 6(a+2 / 3) + 4
f(x) = 9(a²+4a+4 /9 ) - 6a + 12 / 3 + 4
f(x) = 9a² + 36a + 36 / 9 - 6a+12/3 + 4
f(x) = (9a²+36a+36-18a+36+36) / 9
f(x) = (9a² + 18a + 36) / 9
f(x) = 9(a² + 2a + 4) / 9
f(x) = x² + 2x + 4

maka
f(4) = 4² + 2(4) + 4
f(4) = 16 + 8 + 4
f(4) = 28

semoga berguna +_+