1.

If the sum of the roots of the equation ax2 + bx + c = 0 is equal to sum of their squares, then \(\frac{c}{a},\frac{b}{a},\frac{c}{a}\) are in (a) A.P. (b) G.P (c) H.P (d) None of these

Answer»

(a) A.P. 

Let α, β be the roots of the equation ax2 + bx + c = 0. 

Then, α + β = \(-\frac{b}{a}\) , αβ = \(\frac{c}{a}\)

Also, given α + β = α2 + β2  ⇒ α + β = (α + β)2 - 2αβ

⇒ \(-\frac{b}{a}\) = \(\bigg(-\frac{b}{a}\bigg)^2\) - \(\frac{2c}{a}\)

⇒ – ba = b2 – 2ac ⇒ b2 + ab = 2ac 

⇒ b (b+ a) = 2ac ⇒ \(\frac{b}{c}\) + \(\frac{a}{c}\) = \(\frac{2a}{b}\)

 \(\frac{c}{a},\frac{b}{a},\frac{c}{a}\) are in A.P.



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