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JEE Mains · Maths · STD 11 - 4.2 Quadratic equations and inequations

ધારો કે \(P_n=\alpha^n+\beta^n, n \in \mathbf{N}\). જો \(P_{10}=123, P_9=76\), \(P_8=47\) અને \(P_1=1\) હોય, તો \(\frac{1}{\alpha}\) અને \(\frac{1}{\beta}\) બીજ ધરાવતું દ્વિઘાત સમીકરણ __________ છે.

  1. A \(x^2-x+1=0\)
  2. B \(x^2+x-1=0\)
  3. C \(x^2-x-1=0\)
  4. D \(x^2+x+1=0\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(x^2+x-1=0\)

Step-by-step Solution

Detailed explanation

\begin{aligned} & \alpha^{10}+\beta^{10}=123 \\ & \alpha+\beta=1 \\ & \alpha^9+\beta^9=76 \\ & \alpha^8+\beta^8=47 \\ & P_{10}=P_9+P_8 \\ & x^2=x+1 \Rightarrow x^2-x-1=0 \\ & \alpha+\beta=1, \alpha \beta=-1 \\ & \frac{1}{\alpha}+\frac{1}{\beta}=\frac{\alpha+\beta}{\alpha…

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