Question

请问一下这一题怎么写？

Answer 1

解：原式=[(a-3)-2b)][(a-3)+2b]
=(a-3)²-4b²
=a²-6a+9-4b²

追问

请问一下这一题怎么写？

急急急

追答

M-N
=(x²+2x+1)(x²-2x+1)-(x²+x+1)(x²-x+1)
=(x+1)²(x-1)²-[(x²+1)+x][(x²+1)-x]
=[(x+1)(x-1)]²-[(x²+1)²-x²]
=(x²-1)²-(x²+1)²+x²
=(x^4-2x²+1)-(x^4+2x²+1)+x²
=x^4-2x²+1-x^4-2x²-1+x²
=-3x²＜0
所以，M＜N