1.
1+a+b+(a+b)²/4
=[1+(a+b)/2]²
=(a+b+2)²/4
2.
(m+n)-4n²是不是漏平方符号了?
3.
25(3x-y)²-36(3x+y)²
=[5(3x-y)+6(3x+y)][5(3x-y)-6(3x+y)]
=(33x+y)(-3x-11y)
=-(33x+y)(3x+11y)
4.
7.77²+4.46*7.77+2.23²
=(7.77+2.23)²
=10²
=100
5.
(a²+b²-c²)²-4a²b²
=(a²+b²-c²+2ab)(a²+b²-c²-2ab)
=[(a+b)²-c²][(a-b)²-c²]
=(a+b+c)(a+b-c)(a-b+c)(a-b-c)
如果不懂,祝学习愉快!