The distance formula to find the length of the sides... opposite sides equal it could be a rectangle or parallelogram all sides equal, square or rhombus adjacent equal, kite and then the slope is used to check angles if the product of the 2 lines in -1 the lines are perpendicular (right angle) the slopes of 2 lines are the same the sides are parallel. Hope it helps.
Let smaller no be x and bigger be y
- x+y=39--(1)
- 3x=y+81
- y=3x-81
- y=3(x-27)--(2)
Put it in eq(1)
- x+3(x-27)=39
- x+3x-81=39
- 4x=81+39
- 4x=120
- x=30
Now
The numbers are 9 and 30
