25 points
verify that parallelogram abcd with vertices a(-5,-1) , b(-9,6), c(-1,5) and d(3,-2) is a rhombus by showing that it is a parallelogram with perpendicular diagonals.

if you could show all the steps you used

If the slope of AB = CD and BC = AD it's a parallelogram:

Slope of AB = 6+1 / -9+5 = -7/4

CD = -2-5 / 3+1 = -74

These are equal.

BC = 5-6 / -1 +9 = -1/8

AD = -2 +1 / 3+5 = -1/8

These are also equal so it is a parallelogram.

Now to find if the diagonals are perpendicular find the slope of the perpensicular points:

AC = 5 +1 / -1 +5 = 6/4 = 3/2

BD = 6+2 / -9 -3 = 8/-12 = -2/3

Because BD is the reciprocal of AC, this means they are perpendicular.

And because AB is not perpendicular to AD ( AB and AD are not reciprocals) it is a rhombus.

i think it would be 42cm