Question

已知x分之1+y分之1=5 求x+xy+y分之3x-5xy+3y 的值

Answer 1

x分之1+y分之1=5两边乘以xy就得出Y+X=5XY

所以X+XY+Y就等于6XY
然后3X-5XY+3Y就等于15XY
结果就是6分之15
就是3分之5

Answer 2

1/x+1/y=5
二边同乘xy得y+x=5xy
(3x-5xy+3y )/(x+xy+y)
=(3(x+y)-5xy)/(x+y+xy)
=(15xy-5xy)/(5xy+xy)
=5/3