Question

what is perametric equation?

Answer 1

by definition, a parametric equation, is an equation which contains a quantity, called the parameter. That quantity can not to be considered a variable. Sometimes a parametric equation can contain one or more parameters.
For example a parameter can be the ratio between two areas of two geometric shapes.

Answer 2

Two areas of two geometric shapes how?explain please

Answer 3

for example sometimes we have to solve this type of problem, here is the text:
"After to have wrote the equations of the parabolas, whose axes are parallelt o the y-axis, and they pass at point (0,0) (namely the origin of the cartesian system), and whose vertices of those parabolas are V=(2,-2) and V'=(2,-1), and let's call with A the further point of intersection between those parabolas..
Determine on those arcs OA 2 points, say M and N which have the same x-coordinate, such that the ration between the area of the triangle MNO and the area of the triangle MNA is equal to k"

Now we can consider the quantity k as a parameter of our problem.