### 2.42.17 Add a row to another row : `rowAdd`

`rowAdd` takes three arguments : a matrix *A* and two integers
*n*1 and *n*2.

`rowAdd` returns the matrix obtained by replacing in *A*, the row of index
*n*2 by the sum of the rows of index *n*1 and *n*2.

Input :

`rowAdd([[1,2],[3,4]],0,1)`

Output :

`[[1,2],[4,6]]`