Question

Известно что, a + b = 7, и ab = -3, найти (a-b)²

Answer 1

$(a - b)^{2} = {a}^{2} + {b}^{2} - 2ab \ {(a + b)}^{2} = {a}^{2} + {b}^{2} + 2ab \ {(a - b)}^{2} = {(a + b)}^{2} - 4ab = \ {7}^{2} + 4 times 3 = 49 + 12 = 61$