Full question attached:
Mickey simplified the expression below. He then checked his work by substituting 4 for x. He noticed his two values were not equal. What was Mickey’s error when simplifying?
Expression: 2x^2 - 4x - 9 - x^2 + 2x + 3
Simplified expression: x^2 - 6x - 6
ANSWER CHOICES:
Mickey should have added –4 and 2 when combining the coefficients of the x terms.
Mickey should have added 2 and 1 when combining the x^2 terms.
Mickey should have added 9 and 3 when combining the constant terms.
Mickey should have added –4 and –1 when combining the x terms.
Answer
Mickey should have added –4 and 2 when combining the coefficients of the x terms.
Explanation:
To simplify an expression means to group and organize the expression in a such a way that it becomes more understandable, and can now easily be solved
Given the expression 2x² - 4x - 9 - x² + 2x + 3 to simplify
We first group and find like terms and then add and cancel out
2x²-x²- 4x+2x - 9+ 3
=x²-2x-6
Mickey did not add the coefficients -4 and +2 for x terms in the expression, instead it looked like he added 4+2 as the coefficients
Therefore the correct option is
Mickey should have added –4 and 2 when combining the coefficients of the x terms.
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