Let A(-2,-1), B(1,0), C( , ) and D( , ) be the vertices of a parallelogram ABCD. If the point C lies on 2x-y=5 and the point D lies on 3x-2y=6, then the value of | + + + | is equal to .
Answer
32
Solution
Diagonals of a parallelogram bisect each other: mid-point of AC = mid-point of BD
[figure]
( -2, -1)=( +1, ) = -3, = -1
C on 2x-y=5: 2 - =5
D on 3x-2y=6: 3( -3)-2( -1)=6 3 -2 =13
=-3, =-11, =-6, =-12
| + + + |=|-32|=32
Answer: 32