Carlos solved the equation below for x using inverse operations. His solution is x = 6.5. What mistake did Carlos make and how could he have checked his solution to know for certain that his answer is correct?

1 answer

To determine the mistake Carlos made while solving the equation, we first need to identify the original equation he was solving. Since we don’t have the equation presented, we can discuss a general approach to how he might have arrived at the solution and common errors to look out for.

Assuming Carlos made a mistake involving an algebraic operation, possible mistakes could include:

  1. Incorrect arithmetic operations: He might have added or subtracted incorrectly at some point in the process.
  2. Misapplication of inverse operations: If he was supposed to multiply or divide but confused those operations, that could lead to an incorrect solution.

Checking the solution:

To check if \( x = 6.5 \) is indeed the solution, Carlos should substitute \( 6.5 \) back into the original equation. Here’s a general process for checking:

  1. Substitute: Replace \( x \) in the original equation with \( 6.5 \).
  2. Evaluate: Calculate both sides of the equation to see if they are equal.
  3. Compare: If both sides of the equation are equal after substitution, then \( x = 6.5 \) is the correct solution. If not, then Carlos made a mistake.

Example:

Suppose the equation was \( 2x + 3 = 16 \).

  1. Carlos solved for \( x \) and found \( x = 6.5 \).
  2. Checking:
    • Substitute \( x \) back: \( 2(6.5) + 3 = 13 + 3 = 16 \).
    • The left side equals the right side, so in this case, Carlos would be correct.

If it's incorrect:

If the equation was somewhere else, for instance \( 2x + 3 = 12 \):

  1. The correct solution would be \( x = 4.5 \).
  2. If Carlos found \( x = 6.5 \):
    • Checking: \( 2(6.5) + 3 = 13 + 3 = 16 \) (not equal to 12).
    • Thus, he made a mistake in his solving process (perhaps miscalculating or misapplying operations).

By confirming through substitution, Carlos could identify any mistakes in his solution process and rectify them for future problems.