Your answer would be - 3/10
1. Perfect square trinomials, are 2nd degree polynomials, of the form

so that

, which can be written as perfect squares.
2. For example

3. Thus

are perfect square trinomials.
4.

5. In the first case -b=20, so b=-20. In the second case, -b=-20, so b=20.
6. b∈{-20, 20}
Distance between two points, d, is given by

where: (x1, y1) = (8, 2) and (x2, y2) = (3, 8)