Bài 1 : Rút gọn
A= 3(x-1)2-(x+1)2+2(x-3)(x+3)-(2x+3)2-(5-20x)
B= 5x(x-7)(x+7)-x(2x-1)2-(x3+4x2-246x)-175
C= -2x(3x+2)2+(4x+1)2+2(x3+8x+3x-2)-(5-x)
D= (5x-2)2-(6x+1)2+11(x-2)(x+2)-16(3-2x)
E= 4x(x+3)-(x-5)2-3(x+1)2+(2x+2)2-(4x+5)
F= (2x-3)(x+2)(x-2)-2(x+3)-(x+4)3+(x-3)(x2+3x+9)+9x2+110x