Question

Упростите выражение : 2a(3a-5)-(a-3)(a-7)​

Answer 1

$2a(3a - 5) - (a - 3)(a - 7) = 2a \times 3a - 2a \times 5 - (a \times a -a \times 7 - 3 \times a + 3 \times 7) = \\ = 6 {a}^{2} - 10a - ( {a}^{2} - 7a - 3a + 21) = \\ = 6 {a}^{2} - 10a - {a}^{2} + 7a + 3a - 21 = \\ = 5 {a}^{2} - 21$