Question

If the difference of the roots is equal to their product in equation ax²+bx+c=0 then -

(a) b²-4ac=a²
(b) b²-4ac=c²
(c) b²-4ac>c²
(d) b²-4ac>a²

Answer 1

Two roots will be equal if the graph touches the x-axis and value of expression will be minimum at the vertex (minimum ) of graph formed by equation ax² + bx + c = 0.

For Maxima or minima, derivative of expression = 0.

=> dy/dx = 2ax + b = 0

=> x = -b/2a.

:-)