D is a notation for differential. There is a d2 in your formula because in the numerator there are two differentials. The formula is thus the second derivative of a function with respect to two variables.
Answer:
Step-by-step explanation:
Given
There are 28 students in a class out of which
13 are boys so the remaining 15 are girls
Ratio of girls to boys in the class
It’s c counting your heartbeats
<h2>1)</h2>

This must be true for some value of x, since we have a quantity squared yielding a positive number, and since the equation is of second degree,there must exist 2 real roots.

<h2>2)</h2>
Well he started off correct to the point of completing the square.
