Tìm x ( sử dụng các hằng đẳng thức )
a, 2x ( 2x + 5 ) - 4x ( x - 3 ) = 7
b, ( x + 2 ) ( x - 2 ) - ( x + 1 )\(^2\) = 2
c, ( x + 2 ) ( x - 1 ) - ( x + 3 ) ( x - 2 ) = 0
d, x\(^2\) - ( x - 1 )\(^2\) = 4
e, ( 2x + 3 ) ( 2x - 3 ) - ( 2x - 1 )\(^2\) = 6
f, ( x - 1 )\(^2\) - 25 = 0