kak,,tolong bantuin ya..,sekalian caranya,.

Biaya x produk = 9000 + 1000x + 10x^2
Harga jual x produk = 5000x
Laba = harga jual - biaya
L(x) = 5000x - (9000 + 1000x + 10x^2)
L(x) = -9000 + 4000x - 10x^2
L'(x) = 4000 - 20x = 0
=> -20x = -4000
=> x = 200
Jadi laba maksimum
L(200) = -9000 + 4000(200) - 10(200)^2
= -9000 + 800.000 - 400.000
= 391.000