I'm stuck on this problem also
find the perimeter of the polygon with the vertices x(-1,3), y(3,0), and z(-1,-2). round the answer to the nearest hundredth

The perimeter is 14.47
 
Since you have 3 vertices, the polygon you have is a triangle. The sides of the triangle will be XY, XZ, and YZ. Just use the pythagorean theorem to calculate the length of each side and then add the lengths together for the result. Side XY = sqrt( (-1-3)^2 + (3-0)^2) = sqrt(16+9) = sqrt(25) = 5 Side XZ = sqrt ( (-1-(-1))^2 + (3-(-2))^2) = sqrt(0+25) = sqrt(25) = 5 Side YZ = sqrt( (3-(-1))^2 + (0-(-2))^2) = sqrt(16 + 4) = sqrt(20) = 4.47 Now add the length of each side together 5 + 5 + 4.47 = 14.47