Tolong isiin sama caranya juga yahh

y = a(x - x1)(x - x2)
3 = a(0 + 1)(0 - 3)
3 = -3a
a = -1

y = -1(x + 1)(x - 3)
y = -1(x² - 2x - 3)
y = -x² + 2x + 3