若(x的平方-y的平方)(x+y)=(x-y)(x的平方+axy+y的平方) 则a的值为()

来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/18 21:54:09
若(x的平方-y的平方)(x+y)=(x-y)(x的平方+axy+y的平方)则a的值为()若(x的平方-y的平方)(x+y)=(x-y)(x的平方+axy+y的平方)则a的值为()若(x的平方-y的平

若(x的平方-y的平方)(x+y)=(x-y)(x的平方+axy+y的平方) 则a的值为()
若(x的平方-y的平方)(x+y)=(x-y)(x的平方+axy+y的平方) 则a的值为()

若(x的平方-y的平方)(x+y)=(x-y)(x的平方+axy+y的平方) 则a的值为()
(x^2-y^2)(x+y)
=(x-y)(x+y)(x+y)
=(x-y)(x+y)^2
=(x-y)(x^2+2xy+y^2)
=(x-y)(x^2+axy+y^2)
因此a=2
如果认为讲解不够清楚,

(x²-y²)(x+y)=(x-y)(x²+axy+y²)
(x-y)(x+y)²-(x-y)(x²+axy+y²)=0
(x-y)[(x+y)²-(x²+axy+y²)]=0
(x-y)(x²+2xy+y²-x²-axy-y²)=0
(2-a)xy(x-y)=0
对于任意实数x,y,等式恒成立,只有2-a=0
a=2

左边=(x+y)²(x-y)
=(x-y)(x²+2xy+y²)
所以a=2

(x^2-y^2)(x+y)=(x-y)(x^2+axy+y^2)
(x+y)(x-y)(x+y)=(x-y)(x^2+axy+y^2)
(x+y)^2=(x^2+axy+y^2)
(x^2+2xy+y^2)=(x^2+axy+y^2)
a=2

都分解开,就出来了,得A=2