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.
1. Brianna's thinking is incorrect because of course, when x is 0, the expression will equal whatever value isn't an x term. To find equivalent expression, you actually need to find which expressions have the same amount of x terms and the same value.
2. Expressions A and C are equivalent.
3. Expression A can be simplified, as you can do 9x - 3x = 6x, so your final expression would be 6x - 4. Expression C can also be simplified with 5x + x = 6x, which can then also be written as 6x - 4. This means both expressions have the same amount of x terms, and the same value, so they are equivalent.
