If A (–2, –1), B (a, 0), C (4, b) and D (1, 2) are the vertices of a parallelogram. Find the values of a and b. [3 MARKS]
Formula: 1 Mark
Application: 1 Mark
Answers: 1 Mark
We know that the diagonals of a parallelogram bisect each other.
∴ The coordinates of the mid-point of AC = The coordinates of the mid-point of BD i.e.
If A(x1,y1),B(x2,y2),C(x3,y3) and D(x4,y4) are the vertices of parallelogram ABCD, Then
x1+x32,y1+y32=x2+x42,y2+y42
⇒(−2+42,−1+b2)=(a+12,0+22)
⇒(1,b−12)=(a+12,1)
⇒a+12=1 and b−12=1
⇒a+1=2 and b−1=2
⇒a=1 and b=3