An expansion that multiplies only the variable changes the equation. To diagnose it, compare the grouped expression with the attempted line, term by term. An AI math solver can help explain the mismatch, but agreement with its final answer does not establish that your transformation was valid.

Take this example: solve 3(x-2)=12.

Check the problem that reached the solver

Suppose your first expansion is 3x-2=12. The variable has been multiplied by three, but the constant has been left unchanged. This is the first wrong line. Any later arithmetic performed correctly on it will still solve a different equation. Leave this attempt beside the original so you can inspect exactly what changed.

Circle the constant term.

A useful question for the solver is: “I expanded the left side this way. Which term changed incorrectly, and how should the outside factor apply to it?” Request the explanation of that one transformation before reading the remaining solution.

First compare the solver’s input with your worksheet. A missing bracket or a faint minus sign can turn a photo upload into a different problem before the algebra begins. With short notation, typing can make that comparison easier. For handwriting, include both the original equation and your attempted line, clearly separated.

On its current site, MathSolver advertises typed problems, photo and image inputs, PDF upload, step explanations and follow-up questions. Those features offer a way to ask about this mismatch. The site also warns that its answers can contain mistakes, so a generated explanation still needs a mathematical check.

Upload only the relevant work, excluding names and student numbers. For assessed work, follow the assignment’s rules: permission to use an explanation in private practice does not imply permission during a test.

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Compare the two left sides

The correct expansion is 3x-6=12. Three multiplies both terms inside the brackets. The constant is negative six because three multiplies negative two. In the attempted line, that multiplication never happened.

You can expose the mismatch without solving for the unknown. Evaluate the two left sides at zero: the original grouped expression gives negative six, while the attempted expansion gives negative two. These are different values, so the expansion cannot be an equivalent replacement. Zero is a test input here, not a proposed solution to the equation. One counterexample disproves equivalence; agreement at one input would not prove it.

With the expansion repaired, adding six to both sides gives 3x=18, and dividing both sides by three gives x=6. A solver might instead divide the original equation by three before expanding. That route is valid too. Different-looking steps are not necessarily errors; the question is whether each operation preserves the set of solutions.

Substitution into the original equation gives 3(6-2)=12. The grouped expression now evaluates to twelve. Substituting into the wrong intermediate line would check the altered problem, which is why the original equation remains the reference.

This separates three faults that can otherwise look alike. A transcription error requires correcting the input. An invalid expansion requires repairing the algebraic operation. If the expansion is correct but the next addition is wrong, the fault is arithmetic: redo that calculation rather than abandoning distribution. A correct final value alone cannot identify which of these occurred earlier.

An explanation that says only “distribute” may leave the missing multiplication unexplained. Look for an account of both resulting terms, including the sign of the constant. If the explanation contradicts that calculation, compare it with a textbook example or have a teacher examine the two lines.

Change the coefficient before reading the answer

Try 4(x-3)=20 on paper before reading the answer section below. Predict the constant in the expanded expression, then write the expansion and solve. This nearby equation changes the values while keeping the same operation visible.

The diagnostic question is specific: did the outside factor reach the constant as well as the variable? A constant with the right sign but the wrong size points to a multiplication error. A positive constant would point to a sign error. Neither needs a new solution method.

Compare the constant, then the solution

The correct expansion is 4x-12=20, and the solution is x=8. If your constant differs, inspect the multiplication first. If your expansion matches but your answer differs, compare the subsequent arithmetic and substitution into the original equation.

Your error note can now name the operation that failed: “I multiplied the variable but left the constant unchanged.” That is more precise than “I got the wrong answer.” Beside it, record the correction: the outside factor multiplies every term in the group.

The next time you remove brackets, follow the outside factor to each term before moving to the next line.