Let a and b be mxn and r xs matrices respectively. use summation notation to define ( the ij" entry of the product ab. explain carefully why we need n=r for this definition to make sense.

Afruit stand has to decide what to charge for their produce. they need $10 for 4 apples and 4 oranges. they also need $15 for 6 apples and 6 oranges. we put this information into a system of linear equations. can we find a unique price for an apple and an orange?

What term best describes a line ans a point that lie in the same plane

Find the exact value of each of the following. in each case, show your work and explain the steps you take to find the value. (a) sin 17π/6 (b) tan 13π/4 (c) sec 11π/3