What is the perimeter of the polygon defined by the points a(12, 20), b(20, 20), c(20, 8), and d(12, 8)? a 64 units b 144 units c 84 units d 40 units

  d.  40 units

Step-by-step explanation:

The length of the horizontal side of this rectangle on the line y=20 is the difference of the x-coordinates, 12 and 20, so is 8. The length of the vertical side on the line x=20 is the difference of the y-coordinates, 20 and 8, so is 12.

Two sides are of length 8 and two are of length 12. The perimeter is the sum of the side lengths, so is ...

  P = 2·8 +2·12 = 40 . . . units

"standard form:

3x2 + 14x − 10 = 0

solutions based on quadratic formula:

x1   = −14 − √ 142 − 4×3×(−10) /   2×3   = −14 − 2 × √ 79 /   6   ≈ −5.296

x2   = −14 + √ 142 − 4×3×(−10) /   2×3   = −14 + 2 × √ 79 /   6   ≈ 0.629