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Is matrix addition commutative for matrices of the same dimensions?

Yes, matrix addition is commutative. For any two matrices A and B with the same dimensions, A+BA + B equals B+AB + A. This holds because scalar addition of real numbers is itself commutative, so swapping the order of entries before summing them does not change the result.

Conditions

  • Matrices A and B must have identical dimensions.
  • Entries are real numbers.

Reasoning, step by step

  1. Take two matrices A and B of size m×nm \times n.
  2. Compute C=A+BC = A + B by summing A_ij + B_ij.
  3. Compute D=B+AD = B + A by summing B_ij + A_ij.
  4. Apply commutativity of real numbers: A_ij + B_ij = B_ij + A_ij.
  5. Conclude C and D are identical matrices.

Example

The video displays A+BA+B and B+AB+A for specific 2×32\times 3 matrices. Both orders yield the result [[6, -7, 8], [11, 2, -3]], proving visually that order does not matter.

Common misconceptions

  • Confusing matrix addition with matrix multiplication (which is generally NOT commutative).
  • Thinking commutativity depends on the values inside the matrices rather than just their dimensions.

Watch the explanation

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Answers are generated from source material and independently checked. Consult the original video or creator if something is unclear.