Q.If the roots of the equation \( ax^2+bx+c=0 \,(a\ne 0) \) are real and equal, then (a) \(c=\cfrac{-b}{2a}\) (b) \(c=\cfrac{b}{2a}\) (c) \(c= \cfrac{-b^2}{4a}\) (d) \(c = \cfrac{b^2}{4a}\)
Answer: D
As the roots of the equation \(ax^2+bx+c = 0 (a≠ 0) \) are real and equal, then the discriminant:
\(b^2-4ac=0\)
or, \(-4ac=-b^2\)
or, \(c=\cfrac{b^2}{4a}\)
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