初一数学（10）

x(x+2y-a)+y(y-a)+1

(x+2)(x-5)

x(x-y-1)-2y(y+1)

x(x+1)-2y(2y-1)

1.（x+y)(x+y)-a(x+y-1)
=(x+y)^2-a(x+y)+a
=[x+y-(a+√(a^2-4a)/2][x+y-(a-√(a^2-4a)/2]
2.x*x-3xy-10y*y
=(x-5y)(x+2y)
3.x*x-xy-2y*y-x-y
=x^2-y^2-xy-y^2-x-y
=(x+y)(x-y)-y(x+y)-(x+y)
=(x+y)(x-y-y-1)
=(x+y)(x-2y-1)
4.x*x-4y*y+x+2y
=(x+2y)(x-2y)+(x+2y)
=(x+2y)(x-2y+1)

1.（x+y)(x+y)-a(x+y-1)
解:
原式=（x+y)(x+y)-a(x+y)+a
=(x+y)(x+y-a)+a

2. x²-3xy-10y²
解:
原式=(x²+2xy)-(5xy+10y²)
=x(x+2y)-5y(x+2y)
=(x+2y)(x-5y)

3. x²-xy-2y²-x-y
解:
原式=x²+xy-2xy-2y²-x-y
=x(x+y)-2y(x+y)-(x+y)
=(x+y)(x-2y-1)

4. x²-4y²+x+2y
解:
原式=(x+2y)(x-2y)+(x+2y)
=(x+2y)(x-2y+1)

平方符号:只要输入"& s u p 2"就行了(中间的空格去掉).

1.（x+y)(x+y)-a(x+y-1)=(x+y-a/2+√