Упростите выражение: a) 6,2x² - (3,8x + 2,7x²); б) 2,5 - (y² + 3) - (1,2 – 0,8y²).

a) $$6.2x^2 - (3.8x + 2.7x^2) = 6.2x^2 - 3.8x - 2.7x^2 = 3.5x^2 - 3.8x$$ б) $$2.5 - (y^2 + 3) - (1.2 - 0.8y^2) = 2.5 - y^2 - 3 - 1.2 + 0.8y^2 = -0.2y^2 - 1.7$$