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For the system 5x + 6y = 12 and y = (2/3)x - 1, which method is more convenient, and why?
AElimination, since both equations are in standard form
BGraphing, since the lines are perpendicular
CSubstitution, since one equation is already solved for y
DSubstitution, since both coefficients of x are equal
Answer & Solution
Correct answer: C. Substitution, since one equation is already solved for y
1. The second equation is already solved for y, expressed directly in terms of x.
2. When one equation is already solved for a variable like this, substitution is the more convenient method to use.
3. Elimination would require extra work rewriting the second equation into standard form first, and the two equations do not share equal x-coefficients.
_Source: OpenStax Elementary Algebra (CC BY 4.0), Ch 5 "Systems of Linear Equations", section 5.3 Solve Systems of Equations by Elimination_
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