Упростите выражение:
1) $(9a - 2)(9a + 2) + 18a^2$;
2) $25m^2 - (5m - 7)(5m + 7)$;
3) $(b + 7)(b - 4) + (2b - 6)(2b + 6)$;
4) $4x(3x - 10y) - (4x + y)(4x - y)$.
$(9a - 2)(9a + 2) - 18a^2 = 81a^2 - 4 - 18a^2 = 63a^2 - 4$
$25m^2 - (5m - 7)(5m + 7) = 25m^2 - (25m^2 - 49) = 25m^2 - 25m^2 + 49 = 49$
$(b + 7)(b - 4) + (2b - 6)(2b + 6) = b^2 + 7b - 4b - 28 + 4b^2 - 36 = 5b^2 + 3b - 64$
$4x(3x - 10y) - (4x + y)(4x - y) = 12x^2 - 40xy - (16x^2 - y^2) = 12x^2 - 40xy - 16x^2 + y^2 = -4x^2 - 40xy + y^2$
Пожауйста, оцените решение
