tolong ane gan diketahui (f-g) (x) = x³+3x³-8x tentukan f(x) jika 9 (x) = x+1

x³ + 3x³ - 8x
= (x+1)³ + 3(x+1)³ - 8(x+1)
= (x+1)³ + (3x+3)³ - (8x+8)

*) (x+1) (x+1) (x+1)
= x^2 + x + x + 1 (x+1)
= x^2 + 2x + 1 (x+1)
= x^3 + x^2 + 2x^2 + 2x + x + 1
= x^3 + 3x^2 + 3x + 1

*) (3x+3) (3x+3) (3x+3)
= 9x^2 + 9x + 9x + 9 (3x+3)
= 9x^2 + 18x + 9 (3x+3)
= 27x^3 + 27x^2 + 54x^2 + 54x + 27x + 27
= 27x^3 + 81x^2 + 81x + 27
= x^3 + 3x^2 + 3x + 1

makaaa....
= x^3 + 3x^2 + 3x + 1 + x^3 + 3x^2 + 3x + 1 - (8x + 8)
= 2x^3 + 6x^2 + 6x + 2 - 8x - 8
= 2x^3 + 6x^2 - 2x - 6
disederhanakan menjadi
x^3 + 3x^2 - x - 3