alleryStart learning →What is the first step of the substitution method for a system of two rules in two unknowns?
AAdd the two rules together straight away
BDraw both lines and read off the crossing
CMultiply both rules by the same number
DRearrange one rule to give one unknown
Answer & Solution
Correct answer: D. Rearrange one rule to give one unknown
1. Substitution works by replacing one unknown with an expression in the other.
2. To have something to substitute, one rule must first be rearranged to give one unknown on its own.
3. That rearranged expression is then put into the second rule.
4. Adding the rules straight away belongs to the addition method, so option A names a different approach.
_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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