Determine whether the 4 points (2,1), (-1,5),(1,5) and (-2,-1) are the vertics of a parallelogram

Best answer that i found on yahoo ok   set :   x= length of 2nd piece in cm  x- 3= length of 1st piece in cm  x-4= length of 3rd piece in cm  then since you know they all came from the 20 cm ribbon you add them together and set them equal to 20x+ x-3 +x-4 = 20  3x - 7= 20  3x= 27  x= 9  the shortest piece is the third piece which is x- 4  x-4  9-4 = 5  the length of the smallest piece is 5 cm.  the other lengths are  9 cm  6 cm

The answer is 225 miles per 4.5 hours. hope this ; )

Recall that area of the triangle is 1/2*(base)*(height)1/2*(13)*(17) = 110.5the answer is 110.5