Three of the vertices of quadrilateral MARY are M (-3,1), A(3,3), and R(5,7). Find the coordinates of Y, such that, quadrilateral MARY is a parallelogram.

Use coordinate geometry to prove that MARY is a parallelogram.

9514 1404 393

  Y = (-1, 5)

Step-by-step explanation:

The diagonals of a parallelogram bisect each other, so have the same midpoint. That is ...

  (M +R)/2 = (A +Y)/2

  Y = M + R - A . . . . . . multiply by 2 and subtract A

  Y = (-3, 1) +(5, 7) -(3, 3) = (-3 +5 -3, 1 +7, -3) . . . . . substitute point coordinates

  Y = (-1, 5)

Coordinate geometry was used to find Y that makes MARY a parallelogram. The fact that there is a solution is proof enough that MARY is a parallelogram.

_____

Your teacher may expect the "proof" to be either or both of ...

Given the method used above, both of these are unnecessary. However, in the interest of completeness, we will demonstrate.

Slope and Length of MA

  slope = (3 -1)/(3 -(-3)) = 2/6 = 1/3

  length = √(2²+6²) = √40

Slope and Length of AR

  slope = (7 -3)/(5 -3) = 4/2 = 2

  length = √(4² +2²) = √20

Slope and Length of RY

  slope = (5 -7)/(-1 -5) = -2/-6 = 1/3 . . . . same as opposite side MA

  length = √((-2)²+(-6)²) = √40 . . . . . . . same as opposite side MA

Slope and Length of YM

  slope = (1 -5)/(-3 -(-1)) = -4/-2 = 2 . . . . same as opposite side AR

  length = √((-4)² +(-2)²) = √20 . . . . . .  same as opposite side AR

Opposite sides have the same slopes, so the figure is a parallelogram.

Opposite sides have the same lengths, so the figure is a parallelogram.

a. the are of the rectangle is 18.25

b. 18.25 times two is 36.50

rae me : d

1 x=22.52

2: 65/39=604+39x

65x-39x=604

26x=604

x=604/26

×=23.23