Quantified statement

[kainatzahid75]

find a counter example to prove falisity the quantified statement:
For all x and y (x-2y)^2<x^2+4y^2

 

[Dr.Peterson]

find a counter example to prove falisity the quantified statement:
For all x and y (x-2y)^2<x^2+4y^2

Try expanding the left-hand side and comparing with the right-hand side. That should give you an idea what to try.