🛠️ JEE➗ Maths

Let \({\mathrm{P}}_{\mathrm{n}}={\alpha }^{\mathrm{n}}+{\beta }^{\mathrm{n}},\mathrm{n}\in N\). If \({\mathrm{P}}_{10}=1…

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Let \({\mathrm{P}}_{\mathrm{n}}={\alpha }^{\mathrm{n}}+{\beta }^{\mathrm{n}},\mathrm{n}\in N\). If \({\mathrm{P}}_{10}=123,{\mathrm{P}}_{9}=76\), \({\mathrm{P}}_{8}=47\) and \({\mathrm{P}}_{1}=1\), then the quadratic equation having roots \(\frac{1}{\alpha }\) and \(\frac{1}{\beta }\) is :

[JEE Main 2025, 2 Apr (Shift 1)]

a

\({x}^{2}-x+1=0\)

b

\({x}^{2}+x-1=0\)

c

\({x}^{2}-x-1=0\)

d

\({x}^{2}+x+1=0\)

✓ Correct answer: b)

\({x}^{2}+x-1=0\)

Explanation

\({P}_{10}={P}_{8}+{P}_{9}\\ \Rightarrow {x}^{2}=x+1\mathrm{has}\mathrm{roots}\alpha \mathrm{and}\beta \\ \Rightarrow \mathrm{Required}\mathrm{equation}\mathrm{is}\\ {\mathrm{x}}^{2}+\mathrm{x}-1=0\)

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