(a) the instant at which an operator at a terminal enters a request for a response from a computer and
(b) the instant at which the first character of the response is received at a terminal.
In a data system, the system response time is the interval between the receipt of the end of transmission of an inquiry message and the beginning of the transmission of a response message to the station originating the inquiry.
... getting
<math>x^2+\frac{b}{a}x+\frac{b^2}{4a^2}=-\frac{c}{a}+\frac{b^2}{4a^2}.</math>
The left side is now a perfect square; it is the square of (x + ...