Question

Which model represents the factors of 4x2 – 9?

An algebra tile configuration. 5 tiles are in the Factor 1 spot: 2 +x , 3 negative. 5 tiles are in the Factor 2 spot: 2 +x, 3 negative. 25 tiles are in the Product spot in 5 columns with 5 rows. First row: 2 + x squared, 3 negative x. Second row: 2 + x squared, 3 negative x. The last 3 rows are the same: 2 negative x, 3 negative.
An algebra tile configuration. 5 tiles are in the Factor 1 spot: 2 +x , 3 +. 5 tiles are in the Factor 2 spot: 2 +x, 3 +. 25 tiles are in the Product spot in 5 columns with 5 rows. First row: 2 + x squared, 3 + x. Second row: 2 + x squared, 3 negative x. The last 3 rows are the same: 1 + x, 1 negative x, 3 negative.
An algebra tile configuration. 5 tiles are in the Factor 1 spot: 2 +x , 3 +. 5 tiles are in the Factor 2 spot: 2 +x, 3 negative. 25 tiles are in the Product spot in 5 columns with 5 rows. First row: 2 + x squared, 3 + x. Second row: 2 + x squared, 3 + x. The last 3 rows are the same: 2 negative x, 3 negative.

Answer 1

4x^2 − 9 = (2x − 3)(2x + 3) (difference of squares).

The model that matches is the third one — it shows one factor as 2x + 3 and the other as 2x − 3 (i.e. one factor has 2 x-tiles and 3 positive unit tiles, the other has 2 x-tiles and 3 negative unit tiles).