大家来帮忙做题啊！

1. 原式=a^2+2a-15+16
=a^2+2a+1
=(a+1)^2

2. 原式= (x^2-2xy+y^2) -1
=(x-y)^2-1
=(x-y+1)(x-y-1)

1. 原式=a^2+2a-15+16
=a^2+2a+1
=(a+1)^2

2. 原式= (x^2-2xy+y^2) -1
=(x-y)^2-1
=(x-y+1)(x-y-1)
可以啦。

……自己不会做啊……
先把两个括号里面的数字相乘，比如（a-b）(a+b)=a*a+a*b+(-b*a)+(-b*b).
所以1.（a-3)（a+5）+16
=a*a+a*5+(-3)*a+(-3)*5+16
=a^2+2a-15+16
=a^2+2a+1
=(a+1)^2

2. x^2-2xy+y^2 -1
=(x^2-2xy+y^2) -1 --->公式(a+b)^2= a^2 + 2ab + b^2
=(x-y)^2-1 --->同理把x-y看作一个数，a^2-b^2=(a+b)(a-b),这里1可看作1^2
=(x-y+1)(x-y-1)

(1）
（a-3)(a+5)+16
=(a^2+2a-15)+16
=a^2+2a+1
=(a+1)^2

(2)
x^2-2xy+y^2-1
=(x^2-2xy+y^2)-1^2
=(x-y)^2-1^2
=[(x-y)-1][(x-y)+1]
=(x-y-1)(x-y+1)