I used to look at the examples i can’t remember now what it is but look at the examples
We represent a sequence with a formula that lets us find any term in the sequence without knowing any other terms, we are representing the sequence explicitly.
The equation of a circle:

(h,k) - the coordinates of the centre
r - the radius
The midpoint of the diameter is the centre of a circle.
The coordinates of the midpoint:

(x₁,y₁), (x₂,y₂) - the coordinates of endpoints

The centre of the circle is (2,5).
The radius is the distance between an endpoint of the diameter and the centre.
The formula for distance:


The radius is 5.
2x 3.50 = $7 notebook sale 1x 3.00 = $3 pen sale Total sale = $10.00 less $1.00 profit To find percentage of profit $1.00/$10.00 = .10 or 10%