Question

若把分式x+y/x的平方-y的平方中的字母x和y的值同时扩大3倍后,分式的值为1／3,则x－y＝

Answer 1

扩大三倍后,

即(3x+3y)/[(3x)^2-(3y)^2]=3(x+y)/[9(x^2-y^2)]

=(x+y)/[3(x+y)(x-y)]

=1/3(x-y)

=1/3

所以x-y=1