KVPY2011MathematicsParabola
The locus of the point P =( a , b ) where a , b are real numbers such that the roots of x ³+ ax ²+ bx + a =0 are in arithmetic progression is-
Options
- Aan ellipse
- Ba circle
- Ca parabola whose vertex in on the y -axis
- Da parabola whose vertex is on the x -axis
Correct answer
C. a parabola whose vertex in on the y -axis
Step-by-step solution
Let roots - d , , + d Sum 3 =- a =- a 3 product ( ²- d ² )=- a aligned pair product b &= ²- d+ ²+ d+ ²-d² ²-d²=3 b &=2 ²+3 & b-3= 2 9 a² locus x²= 9 2 (y-3) parabola aligned