Question

An irregular polygon with 4 sides is shown.

Answer 1

We know that the sum of the lengths of the sides of a polygon is the perimeter of the polygon, by definition.

Thus, in our case of four sided polygon with the side lengths as a,b,c and d and the perimeter as P, we can write the equation of the perimeter to be as:

$P=a+b+c+d$

Thus, if we have to find the side length, d, given the perimeter, P , and other three sides a,b and c, then we will have to isolate the d in the above equation by subtracting a+b+c from both sides. We will get:

$P-a-b-c=d$

Thus, the the equation that can be used to find the side length, d is:

$d=P-a-b-c$

From the given list Option B is the correct option.

Answer 2

The correct answer would be b) d=P-a-b-c

You would take the perimeter and subtract the 3 known sides from it to find the missing side.