1.21 rounded to the nearest whole number

1.2

1 is the whole number and to round you look one place over, in this case the number one over to the left if 2. If the number to the left is 5 or more you “raise the score” making the number your rounded go up one. If the number is 4 or less, you “let it rest” meaning the number stays the same. Once you round, you drop every number behind the number you used to round. So instead or 1.21 it’s 1.2

Solution. Multiply A B \displaystyle AB AB and B A \displaystyle BA BA. If both products equal the identity, then the two matrices are inverses of each other.