The length of a square can be written with the expression 3x + 1. what expression can be used to represent the perimeter of the square?

perimeter - add up all the sides

4 sides of a square

3x + 1 + 3x + 1 + 3x + 1 + 3x + 1 (or 4(3x+1))

collect like terms

= 12x+4

he used the algebra tiles correctly.

step-by-step explanation:

given : 3x(2x-1)

solution :

since he used algebra tiles .

armando's solution is the same in the solution shown in figure

as he distributed 2x into x and x and wrote them vertically

and also write   -1 vertically

and 3x into x and x and x and wrote it horizontally

performing the multiplication in the algebra tiles we get

and solving the given expression :

3x(2x-1)

since solving the expression using tiles   and solving the expression algebraically we get the same answer

thus   we can choose the first statement as the answer to this problem which is "he used the algebra tiles correctly".