Rút gọn biểu thức: a) 2x(3x²y + 4xy-3); b) x² - 4 - (x + 2)²; c) (x + 2)(x - 2) - (x - 3)(x + 1); d) (x - 2)(x + 2) - (x - 2)(x + 5)

Rút gọn biểu thức
a) 2x(3x²y+4xy-3)
b) x²-4-(x+2)²
c) (x+2)(x-2)-(x-3)(x+1)
d) (x-2)(x+2)-(x-2)(x+5)
e) (6x+1)²+(6x-1)²-2(6x+1)(6x-1)
f) 7a(3a-5)+(2a-3)(4a+1)-(6a-2)²
i) (5y-3)(5y+3)-(5y-4)²
k) (2x+1)²+2(4x-1)+(2x-1)²