Idon't understand it.

perform the indicated operation. (2x + y)^2

4x^2 + 4xy + y^2

Step-by-step explanation:

"(2x + y)^2" is an example of "square of a binomial."  Among the various algebraic rules there is a formula applying here:

(a + b)^2 = a^2 + 2ab + b^2  (square of a binomial, square of the sum of

                                              two numbers)

It would be worth your while to learn this, as well as

(a - b)^2 = a^2 - 2ab + b^2

Applying the rule (a + b)^2 = a^2 + 2ab + b^2 to (2x + y)^2, we get:

(2x)^2 + 2(2x)(y) + y^2, or, after simplification:

4x^2 + 4xy + y^2