Given a + B = 2, ab = - 3, then A-B equals () A. 20B. ±3C. 4D. ±4

Given a + B = 2, ab = - 3, then A-B equals () A. 20B. ±3C. 4D. ±4

According to a + B = 2, ab = - 3, (a-b) 2 = (a + b) 2-4ab, = 4 + 12 = 16, so A-B = ± 4