Tìm x biết: (x + 7)² - x(x - 3) = 12; (2x + 3)² - 4x² = 10; (x + 2)² - (x - 2)(x + 1) = 3; 27x²(x + 1) - (3x + 1)² = -8

(x+7)²-x(x-3) = 12.
(2x+3)²-4x² =10.
(x+2)²-(x-2)(x+1)=3.
27x²(x+1)-(3x + 1)² = -8
(2x + 3)² - 4(x-1)² = 0.
(x+1)(x²-x+1)-x(x²-2) = 4.