初一数学·计算与化简题

1、化简.
51a^n+1·b^n+2·c^n+3/68a^n-1·b^n-2·c^n-3
已经是最简了
2、若x^2n=2,求(2x^3n)²-(3x^n)²的值
=8x^6n-9x^2n
=8(x^2n)³-9x^2n
=8*8-9*2
=46
3、分解因式：a²(x²-y²)+b²(y²-x²)
=a²(x²-y²)-b²(x²-y²)
=(a²-b²)(x²-y²)
=(a+b)(a-b)(x+y)(x-y)