Question

就这几道1.因式分解（要写出解题过程）（x-y)的平方-4（x的平方-y的平方）+4（x的平方+y的平方）2.化简求值：

Answer 1

1.

（x-y)^2-4(x^2-y^2)+4(x^2+y^2)

=(x-y)^2-4[(x^2-y^2)-(x^2+y^2)]

=(x-y)^2-4*(-2y^2)

=(x-y)^2+8y^2

2.

根据题意得:

3x=4y

x=(4y/3)

(3x^2-5xy+2y^2)/(2x^2+3xy-5y^2)

=[3*(4y/3)^2-5*(4y/3)*y+2y^2]/[2*(4y/3)^2+3*(4y/3)*y-5y^2]

=[(48y^2/9)-(20y^2/3)+2y^2]/[(32y^2/9)+(12y^2/3)-5y^2]

=[(48y^2-60y^2+18y^2)/9]/[(32y^2+36y^2-45y^2)/9]

=[(6y^2)/9]/[(23y^2)/9]

=[(6y^2)/9]*[9/(23y^2)]

=[(6y^2)/9]*[9/(23y^2)]

=6/23