Hi,

Given the matrix

A= 1 1 0 1 4

2 0 0 4 7

1 1 1 0 5

1 -3 -1 -10a

determine the value ofsuch that, in a row-echelon form of A, the stairstep reaches the bottom.a

#The answer is a=1 but I have no idea why is it so???...Thanks in advance for any help you are able to provide...