6xy is already in simplest form, unless a typo has occurred in your question.
An algebraic expression is an expression built up from integer constants, variables, and the algebraic operations.
ANSWER

EXPLANATION
Use the Pythagoras Theorem to obtain,

This implies that,


Take the positive square root of both sides to get,


Draw four boxes. Put five balloons in one box with the characters in them and write 1/4 under that box. Then draw five balloons in the other boxes, then draw one big box with the total amount of balloons in them.