tolong di bantu.........

keuntungan = penjualan - modal
keuntungan maks apabila turunan bernilai 0
penjualan = 5000x
modal = 20000 + 1000x + 10x²
keuntungan = 5000x - (20000 + 1000x + 10x²)
misal keuntungan = f(x)
f(x) = 5000x - 20000 - 1000x - 10x²
f'(x) = 5000 - 1000 - 20x = 0
4000 - 20x = 0
20x = 4000
x = 20

maka f(20)
= 5000(20) - 20000 - 1000(20) - 10(400)
= 100000 - 20000 - 20000 - 4000 = 56000 rupiah