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Trivial Solution Calculator

Solve trivial solution problems with clear steps, notation, and a final check.

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Linear algebra

Trivial Solution Calculator explained

The short version

  • A homogeneous system is one where every equation equals zero: Ax = 0.
  • Setting every variable to zero always works, and that is called the trivial solution.
  • The real question is whether any other solution exists, and the determinant answers it.

The formula this page uses

Ax = 0 always has x = 0. Nontrivial solutions exist exactly when det A = 0, that is when rank(A) < number of unknowns.

What each part means

SymbolWhat it means
A — Coefficient matrixThe numbers in front of the unknowns. The right-hand side is all zeros.
x = 0 — Trivial solutionEvery unknown set to zero. It satisfies every homogeneous system, always.
rank(A) — RankThe number of independent equations left after row reduction.
n − rank(A) — Free variablesHow many parameters the solution set needs. Zero free variables means the trivial solution is the only one.

Show your work: a full example

  1. The homogeneous system2x + 3y = 0 and 4x + 6y = 0
  2. Determinant of the coefficient matrix(2)(6) − (3)(4) = 12 − 12 = 0
  3. Zero determinant, so nontrivial solutions existrow reduce to see them
  4. Row 2 minus 2 × Row 10x + 0y = 0, which tells you nothing new
  5. One real equation is left2x + 3y = 0, so x = −1.5y
  6. Write the whole solution set with a parameterlet y = 2t, then x = −3t, so every solution is t(−3, 2)
  7. Check with t = 12(−3) + 3(2) = 0 ✓ and 4(−3) + 6(2) = −12 + 12 = 0 ✓, and t = 0 gives back the trivial solution

A second, different case

  1. A different case: only the trivial solution2x + 3y = 0 and 4x − y = 0
  2. Determinant(2)(−1) − (3)(4) = −2 − 12 = −14
  3. Not zero, so no free variables existthe only solution should be x = y = 0
  4. Confirm by substitution, from the second equationy = 4x
  5. Put that into the first2x + 3(4x) = 14x = 0
  6. Solvex = 0, and therefore y = 0
  7. Picture itthese are two different lines through the origin, and two different lines cross at exactly one point
Copy-ready example

2x + 3y = 0 and 4x + 6y = 0

The homogeneous system

Rank against unknowns decides the whole answer for Ax = 0

SystemUnknowns nRankFree variablesSolution set
[[2, 3], [4, −1]]220only the trivial (0, 0)
[[2, 3], [4, 6]]211a line: t(−3, 2)
[[1, 0, 0], [0, 1, 0], [0, 0, 1]]330only the trivial (0, 0, 0)
[[1, 1, 1]], one equation312a plane through the origin
Any system with n > number of equationsnat most mat least 1nontrivial solutions guaranteed

Three mistakes to check for

What students writeWhy it's wrongDo this instead
Ax = 0 has no solution when det A ≠ 0A homogeneous system can never be inconsistent, because zeros always satisfy it.det A ≠ 0 means the trivial solution is the only one, not that there are none.
Reporting (−3, 2) as the answerThat is one point on a whole line of solutions, and (−6, 4) works just as well.Give the full set: t(−3, 2) for any real t.
Assuming det A = 0 means the system is brokenFor a homogeneous system a zero determinant is the interesting case, because it is exactly when extra solutions appear.Row reduce and read off the free variables.

Questions about the Trivial Solution Calculator

Why is the zero solution called trivial?

Because it takes no work and it tells you nothing. Every homogeneous system has it, so finding it is never the point. The question a problem is really asking is whether anything else also works.

When is a nontrivial solution guaranteed without any calculation?

When there are more unknowns than equations. Three unknowns and one equation leaves two free variables no matter what the numbers are, which is the last row of the table above.

How does this connect to linear independence?

Directly. The columns of A are linearly independent exactly when Ax = 0 has only the trivial solution. A nontrivial solution is a recipe for combining the columns into zero, which is what dependence means.

What changes if the right-hand side is not zero?

Everything. A non-homogeneous system can be inconsistent and have no solutions at all, which a homogeneous one never can. Its full solution is one particular solution plus the homogeneous solution set found here.

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