Question

Brianna’s teacher asks her which of these three expressions are equivalent to each other. Expression A: 9x - 3x - 4 Expression B: 12x - 4 Expression C: 5x + x - 4 Brianna says that all three expressions are equivalent because the value of each one is - 4 when x = 0. Brianna’s thinking is incorrect. Identify the error in Brianna’s thinking. Determine which of the three expressions are equivalent. Explain or show your process in determining which expressions are equivalent in the space provided.

Answer 1

Brianna's thinking is wrong because obviously all of the expressions are going to equal -4 when x is 0 because -4 would be the only value. Also, if x was a different number, the expressions wouldn't be equivalent. The equivalent expressions are A. 9x - 3x - 4, and C. 5x + x - 4. This is because when both are simplified, they equal 6x - 4.