你会做这个初二的数学题么？很难的

x^2-a^2-y^2-2ay
=x^2-(a^2+y^2+2ay)
=x^2-(a+y)^2
=(x+a+y)(x-a-y)

x^2-a^2-y^2-2ay
=x^2-(a^2+2ay+y^2)
=x^2-(a+y)^2
=[x+(a+y)][x-(a+y)]
=(x+a+y)(x-a-y)

x平方-a平方-y平方-2ay，
=x^2-(a+y)^2
=(x+a+y)(x-a-y)

我们可以把a+y看成一个数.

原式=x^2-(a+y)^2=(x+a+y)(X-A-Y)

X*X-A*A-Y*Y-2AY
=X*X-(A*A+Y*Y+2AY)
=X*X-(A+Y)*(A+Y)
=[X-(A+Y)]*[X+(A+Y)]
=(X-A-Y)(X+A+Y)

原式=x2-(a2+y2+2ay)=x2-(a+y)2=你给的答案