The very first one (the very left one)
We are given an equation:

This is an equation of a circle. General form of a circle equation is:

Where:
a = x coordinate of a center
b = y coordinate of a center
r = radius of a circle
Motion detector can detect person anywhere within a boundary. The greatest distance at which detector can detect is at the edge of a circle. That distance, between detector and edge of circle, is equal to radius.
From the equation we have:

The greatest distance at which person can be detected is 4ft.
When a polygon is regular, that means that all of its sides are the same length and all of its angles are the same. A heptagon has seven sides and you know that all of them measure 3 inches. You can find the perimeter by adding all of the side measures together, so 3 + 3 + 3 + 3 + 3 + 3 + 3, or 3 x 7. So, the perimeter of the heptagon is 21 inches.
Is the greatest factor that two or more numbers have in common. One way to find the GCF is to make lists of the factors for two numbers and then choose the greatest factor that the two factors have in common.
The answer is 2/3 because absolute value is always positive and a rational number is a fraction