BITSAT2015MathematicsStraight LinesActual
If the lines p ₁ x + q ₁ y =1, p ₂ x + q ₂ y =1 and p ₃ x + q ₃ y =1 be concurrent, then the points ( p ₁, q ₁ ), (p₂, q₂ ) and (p₃, q₃ )
Options
- Aare collinear
- Bform an equilateral triangle
- Cform a sealene triangle
- Dform a right angled triangle
Correct answer
A. are collinear
Step-by-step solution
The equations of the lines are array l p ₁ x + q ₁ y -1=0 p ₂ x + q ₂ y -1=0 array and p ₃ x + q ₃ y -1=0 As they are concurrent, | array lll p ₁ & q ₁ & -1 p ₂ & q ₂ & -1 p ₃ & q ₃ & -1 array |=0 | array lll p ₁ & q ₁ & 1 p ₂ & q ₂ & 1 p ₃ & q ₃ & 1 array |=0 This is also the condition for the points ( p ₁, q ₁ ), ( p ₂, q ₂ ) and ( p ₃, q ₃ ) to be collinear.