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A pair of values has been worked out for a system. What is the safest way to be sure it is right?
APut it back into both rules and check each
BPut it back into the easier rule of the two
CRedo the same working a second time over
DCompare it with the answer of a classmate
Answer & Solution
Correct answer: A. Put it back into both rules and check each
1. A solution has to satisfy both rules, not just the one it was worked out from.
2. Putting the pair back into each rule tests exactly that.
3. Checking only one rule can pass a wrong pair, since many pairs fit any single rule.
4. Repeating the same working would repeat the same slip, so option C is a weaker check.
_Source: OpenStax College Algebra (CC BY 4.0), Ch 7 "Systems of Equations and Inequalities", section 7.1 Systems of Linear Equations: Two Variables_
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