Question

已知正數x、y滿足x-2y=0，則

x

y

=______；

x2+xy+y2

x2-y2

=______．

Answer 1

由題意，得x=2y；
∴

x

y

=2；

x2+xy+y2

x2-y2

=

(x+y)2-xy

(x+y)(x-y)

=

9y2-2y•y

2y•y

=

7

3

．
故答案為

7

3

．