Integral tentu dari 4 integral 1 (x-5) (x+1) dx

penulisannya gini kali...??
int (x - 5)(x + 1) dx, dari x = 1 sampai x = 4
= int (x² - 4x - 5) dx
= (1/3)x³ - 2x² - 5x
x = {1, 4}
= (1/3)4³ - 2(4)² - 5(4) - [(1/2) - 2 - 5]
= │-145/6│
= 145/6 satuan luas