Question

Let B = −1 1 −3

0 2 3 . Compute the indicated matrix. (If this is not possible, enter DNE in any single blank). BTB

Answer 1

Remember that in the transpose matrix of the matrix A, the entry
`a_(ij)` of A will be the entry
`a_(ji)` of
`A^T`.

Then if

`B=\left[\begin{array}{ccc}-1&1&-3\\0&2&3\end{array}\right]`,
`B^T=\left[\begin{array}{ccc}-1&0\\1&2\\-3&3\end{array}\right]`

Then

`B^TB=\left[\begin{array}{ccc}1&-1&3\\-1&5&3\\3&3&18\end{array}\right]`