Упростите выражение:
а) $(7 - 2x - x^2) - (x - 2)(x + 3)$;
б) $(3m^2 + 3n^2) - (2m + n)(m + 2n)$;
в) u(u + v) − (v − 1)(u − 1).
$(7 - 2x - x^2) - (x - 2)(x + 3) = 7 - 2x - x^2 - (x^2 - 2x + 3x - 6) = 7 - 2x - x^2 - (x^2 + x - 6) = 7 - 2x - x^2 - x^2 - x + 6 = -2x^2 - 3x + 13$
$(3m^2 + 3n^2) - (2m + n)(m + 2n) = 3m^2 + 3n^2 - (2m^2 + mn + 4mn + 2n^2) = 3m^2 + 3n^2 - (2m^2 + 5mn + 2n^2) = 3m^2 + 3n^2 - 2m^2 - 5mn - 2n^2 = m^2 - 5mn + n^2$
$u(u + v) - (v - 1)(u - 1) = u^2 + uv - (uv - u - v + 1) = u^2 + uv - uv + u + v - 1 = u^2 + u + v - 1$
Пожауйста, оцените решение
