Checking Solutions Examples in Math

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Checking Solutions.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Math.

Concept Recap

Checking solutions means substituting candidate values back into the original condition to verify they satisfy it.

Treat your answer as a hypothesis and test it by substituting back into the original equation to verify.

Read the full concept explanation โ†’

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: A candidate value is only a valid solution if substituting it makes the original equation or inequality true.

Common stuck point: Always check against the ORIGINAL equation, not a transformed version โ€” transformed equations may have extra or fewer solutions.

Sense of Study hint: Always plug into the first equation given in the problem statement.

Worked Examples

Example 1

easy
Check whether x = 5 is a solution of 2x - 3 = 7.

Solution

  1. 1
    Substitute x = 5 into the left side: 2(5) - 3 = 10 - 3 = 7.
  2. 2
    Compare with right side: 7 = 7 โœ“
  3. 3
    Yes, x = 5 is a solution.

Answer

Yes, x = 5 is a solution.
Checking a solution means substituting the candidate value and verifying both sides of the equation are equal.

Example 2

medium
Solve \sqrt{x+3} = x - 3 and check for extraneous solutions.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy
Is x = -2 a solution of x^2 + x = 2?

Example 2

medium
Someone solved \frac{x}{x-2} = \frac{2}{x-2} and got x = 2. Is this valid?

Background Knowledge

These ideas may be useful before you work through the harder examples.

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