Respuesta :

You must multiply each element of first row of H and first column of J to get 
a
11 = 4*7 + -2*3 + 5*8 = 28 - 6 + 40 = 62 
You now multiply each element of second row of H and first column of J to get 
a
21 = 6*7 + 1*3 + -3*8 = 42 + 3 - 24 = 21