Tính
1, (5+x)(x-5)
2, (3x+y)^2
3, (x+1)^2
4, (x+3)(x^2-3x+9)
5, (2+3x)^2
6, (x-3)(x+3)
7, (x-1)^3
8, (x-2)(x^2+2x+4)
9, (x^2+2)^2-(x+2)(x-2)(x^2+4)
10, (6x+1)^2+(6x-1)^2-2(1+6x)
11, 3(2^2+1)(2^4+1)(2^8+2)(2^16+1)
12, x(2x^2-3)-x^2(5x+1)+x^2
13, x(x-2)-5x(1-x)-8(x^2-3)