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How is matrix addition defined for two matrices of the same dimensions?

Matrix addition is performed by adding corresponding entries. If two matrices have the same number of rows and columns, their sum is a new matrix where each element (i,j)(i,j) equals the sum of the elements at position (i,j)(i,j) in both original matrices.

Conditions

  • Both matrices must have identical dimensions (same m×nm \times n).

Reasoning, step by step

  1. Verify that Matrix A and Matrix B have the same number of rows and columns.
  2. Identify the entry at row ii, column jj in A (AijA_{ij}) and in B (BijB_{ij}).
  3. Compute the arithmetic sum Aij+BijA_{ij} + B_{ij}.
  4. Place this result in position (i,j)(i,j) of the output matrix C.
  5. Repeat for all positions to form the full sum matrix.

Example

In the video, two 2×32\times 3 matrices are added. The top-left entries 1 and 5 are circled together; their sum 6 becomes the top-left entry of the result. Similarly, -7 and 0 produce -7.

Common misconceptions

  • Believing you can add any two matrices regardless of size.
  • Adding entries from different positions (e.g., first row of A to second row of B).

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