Answer:
B. use multipliers -3 and 2
Step-by-step explanation:
If you're solving the system by "addition," multiplying the equations by the chosen numbers needs to result in opposite coefficients for one of the variables.
<h3>Effect of answer choices</h3>
A. The system becomes ...
- 12x -6y = 21
- 12x -12y = 60
No variable has opposite coefficients.
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B. The system becomes ...
- -12x +6y = -21
- 6x -6y = 30
The y-variable has opposite coefficients. This is a good choice.
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C. The system becomes ...
No variable has opposite coefficients.
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D. The system becomes ...
- 4/3x -2/3y = 7/3
- 3x -3y = 15
No variable has opposite coefficients.
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<em>Additional comment</em>
The simplest "no brainer" solution is to use the coefficients of one of the variables, negating one of them. Multiply each equation by the opposite equation's coefficient. Here, the y-coefficients are -2 and -3, and the multipliers of answer choice B are -3 and 2, consistent with this advice. (The sign of 2 was changed.)
