Question

: Brianna’s teacher asks her which of these three expressions are equivalent to each other. Expression A: 6x + 4 Expression B: 12x + 4 Expression C: 5x + x + 4 Briana says that all three expressions are equivalent because the value of each one is 4 when x = 0. Do you agree or disagree with Brianna?

Answer 1

I disagree with Brianna.

Explanation:

Expression A: 6x + 4

6(0) + 4

4

6(1) + 4

6 + 4

10

6(2) + 4

12 + 4

16

Expression B: 12x + 4

12(0) + 4

4

12(1) + 4

12 + 4

18

12(2) + 4

24 + 4

28

Expression C: 5x + x + 4

5(0) + (0) + 4

4

5(1) + (1) + 4

5 + 1 + 4

10

5(2) + (2) + 4

10 + 2 + 4

16

It is true that when you substitute the “x” in each expression with 0, you get 4. However, when you sustitute a different number, like 1 or 2, you get completely different answers. In order for these expressions to all be equal, they have to all get the same answer each time. Yet, notice how both expressions A and C got the same answer every time. This is because when you simplify expression C, you get 6x + 4 (when you add together 5x and x). Therefore, expressions A and C will always be equivalent.