Question

已知3x+2y=a,2x+3y=b,则(x+y)(x-y)=?？

Answer 1

3x+2y=a,2x+3y=b
两式相加可得
5x+5y=a+b
∴x+y=(a+b)/5
两式相减可得
x-y=a-b
所以
(x+y)(x-y)=(a+b)/5*(a-b)=(a²-b²)/5,2,3x+2y=a 1
2x+3y=b 2
1-2=x-y=a-b
1+2=5x+5y=a+b
x+y=(a+b)/5
(x+y)(x-y)=(a+b)(a-b)/5=...........平方不会打,2,3x+2y+2x+3y=a+b
即 5x+5y=a+b
5（x+y）=a+b
所以 x+y=（a+b）/5···········1
3x+2y-(2x+3y)=a-b
即 x-y=a-b···············2
所以（x+y)(x-y)=(a+b)/5·（a-b）
=（a+b)(a-b)/5
=(a^2-b^2)/5,2,(3x+2y)-(2x+3y)=x+y=a-b:
(2x+3y)-(3x+2y)=y-x=b-a:
(x+y)(x-y)=(a-b)(b-a),1,