Skill: Verify algebraic solutions by substitution

Explanation and Free Practice Resources

Verification by substitution means replacing a variable with a proposed value everywhere it occurs, evaluating both sides of the equation, and determining whether the resulting equality is true. It distinguishes a value that satisfies the entire equation from one that only makes part of an expression appear correct, supporting reliable algebraic reasoning with one-variable equations involving whole numbers, integers, fractions, and decimals; systems, identities, and advanced extraneous-solution analysis are not included.

Detailed Explanation: Verify algebraic solutions by substitution

To verify whether a proposed value solves an equation:

  1. Replace the variable with the proposed value everywhere it appears.
  2. Evaluate the left side.
  3. Evaluate the right side.
  4. Compare the results. If they are equal, the value is a solution.

Example: Check whether x=5x=5 is a solution to

3x+5=203x+5=20

Substitute 55 for xx:

3(5)+5=203(5)+5=20

Evaluate the left side:

15+5=2015+5=20

The equation becomes

20=2020=20

This statement is true, so x=5x=5 is a solution to the equation.

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