This exercise practices spacing, arrays, ellipses and functional
names. The image reads as follows (using appropriate fonts and
symbols, where <diagonal matrix> is a 4x4 array
representing a diagonal matrix with horizontal, vertical and
diagonal ellipses representing omissions):
The set of linear equations:
aixi = bi
<horizontal gap of 2em>
"for all" symbol i = 1,...,n
can be written as a matrix equation:
diag(a)x = b
where x = (x1,...,xn)T,
b = (b1,...,bn)T and
diag(a) = [<diagonal matrix>]
Return