1. explain under what conditions the product ab of two matrices a and b is defined. 2. explain under what conditions the sum a + b of two matrices a and b is defined. 3. what does it mean for a matrix to be non-zero? 4. what matrix does the notation in represent? explain in words, then construct i3. 5. if a matrix a is 3 × 5 and the product ba is 2 × 5, then what is the siz

Mariah is randomly choosing three books to read from the following: 5 mysteries, 7 biographies, and 8 science fiction novels. which of these statements are true? check all that apply. there are 20c3 possible ways to choose three books to read. there are 5c3 possible ways to choose three mysteries to read. there are 15c3 possible ways to choose three books that are not all mysteries. the probability that mariah will choose 3 mysteries can be expressed as . the probability that mariah will not choose all mysteries can be expressed as 1 −