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Consider the quadratic equation $(n^2-2n+2)x^2-3x+(n^2-2n+2)^2=0, n \in \mathbf{R}$. Let $\alpha$ be the minimum value of the product of its roots and $\beta$ be the maximum value of the sum of its roots. Then the sum of the first six terms of the G.P., whose first term is $\alpha$ and the common ratio is $\frac{\alpha}{\beta}$, is :

The correct answer is
$\frac{364}{243}$

Analyzing the Quadratic Equation Coefficients

The given quadratic equation is $(n^2-2n+2)x^2-3x+(n^2-2n+2)^2=0$. Let $k = n^2-2n+2$. We can rewrite this by completing the square:

$k = (n^2-2n+1) + 1 = (n-1)^2 + 1$.

Since $(n-1)^2 \ge 0$ for any real $n$, the minimum value of $k$ is $1$ (when $n=1$). Therefore, $k \ge 1$.

The equation becomes $kx^2 - 3x + k^2 = 0$. For a quadratic equation $Ax^2+Bx+C=0$, the coefficient $A$ must be non-zero. Since $k \ge 1$, $k \neq 0$, and the equation is always quadratic.

Finding the Minimum Product of Roots ($\alpha$)

For the quadratic equation $kx^2 - 3x + k^2 = 0$, the product of the roots is given by $P = \frac{C}{A} = \frac{k^2}{k}$.

Simplifying, we get $P = k$.

We established that $k \ge 1$. The minimum value of $P$ occurs when $k$ is at its minimum.

Therefore, the minimum value of the product of roots is $\alpha = \min(k) = 1$.

Finding the Maximum Sum of Roots ($\beta$)

The sum of the roots for the quadratic equation $kx^2 - 3x + k^2 = 0$ is given by $S = -\frac{B}{A} = -\frac{-3}{k}$.

Simplifying, we get $S = \frac{3}{k}$.

We know that $k \ge 1$. This implies $0 < \frac{1}{k} \le 1$.

Therefore, $0 < \frac{3}{k} \le 3$. The maximum value of $S$ occurs when $\frac{1}{k}$ is maximum, which happens when $k$ is minimum ($k=1$).

Thus, the maximum value of the sum of roots is $\beta = \max(\frac{3}{k}) = 3$.

Calculating the Geometric Progression (G.P.) Sum

We need to find the sum of the first six terms of a G.P.

  • First term, $a = \alpha = 1$.
  • Common ratio, $r = \frac{\alpha}{\beta} = \frac{1}{3}$.
  • Number of terms, $n = 6$.

The formula for the sum of the first $n$ terms of a G.P. is $S_n = a \frac{1 - r^n}{1 - r}$.

Substituting the values:

$S_6 = 1 \cdot \frac{1 - (\frac{1}{3})^6}{1 - \frac{1}{3}}$

$S_6 = \frac{1 - \frac{1}{729}}{\frac{2}{3}}$

$S_6 = \frac{\frac{729 - 1}{729}}{\frac{2}{3}}$

$S_6 = \frac{\frac{728}{729}}{\frac{2}{3}}$

$S_6 = \frac{728}{729} \times \frac{3}{2}$

$S_6 = \frac{364}{729} \times 3$

$S_6 = \frac{364}{243}$

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Similar Questions

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