MCQ
If $\alpha \ne \beta $ but ${\alpha ^2} = 5\alpha - 3$ and ${\beta ^2} = 5\beta - 3$, then the equation whose roots are $\alpha /\beta $ and $\beta /\alpha $ is
  • A
    $3{x^2} - 25x + 3 = 0$
  • B
    ${x^2} + 5x - 3 = 0$
  • C
    ${x^2} - 5x + 3 = 0$
  • $3{x^2} - 19x + 3 = 0$

Answer

Correct option: D.
$3{x^2} - 19x + 3 = 0$
d
(d) ${\alpha ^2} - 5\alpha + 3 = 0$ …..$(i)$

${\beta ^2} - 5\beta + 3 = 0$ …..$(ii)$

From $(i) -(ii),$

==> $({\alpha ^2} - {\beta ^2}) - 5\alpha + 5\beta = 0$

==> ${\alpha ^2} - {\beta ^2} = 5(\alpha - \beta )$$ \Rightarrow \alpha + \beta = 5$

From $(i) + (ii),$

==> $({\alpha ^2} + {\beta ^2}) - 5(\alpha + \beta ) + 6 = 0$

==> $({\alpha ^2} + {\beta ^2}) - 5.5 + 6 = 0$ ==> ${\alpha ^2} + {\beta ^2} = 19$

Then ${(\alpha + \beta )^2} = {\alpha ^2} + {\beta ^2} + 2\alpha \beta $

$ \Rightarrow 25 = 19 + 2\alpha \beta $ $ \Rightarrow \alpha \beta = 3$

then the equation, whose roots are $\frac{\alpha }{\beta }$ and $\frac{\beta }{\alpha }$, is

${x^2} - x\left( {\frac{\alpha }{\beta } + \frac{\beta }{\alpha }} \right) + \frac{\alpha }{\beta }.\frac{\beta }{\alpha } = 0$

==> ${x^2} - x\left( {\frac{{{\alpha ^2} + {\beta ^2}}}{{\alpha \beta }}} \right) + 1 = 0$

$ \Rightarrow {x^2} - x.\frac{{19}}{3} + 1 = 0$

==> $3{x^2} - 19x + 3 = 0$.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

Let $AB$ be a chord of the circle ${x^2} + {y^2} = {r^2}$ subtending a right angle at the centre. Then the locus of the centroid of the $\Delta PAB$ as $P$ moves on the circle is
If ${x_n} = \frac{{1 - 2 + 3 - 4 + 5 - 6 + ..... - 2n}}{{\sqrt {{n^2} + 1} + \sqrt {4{n^2} - 1} }},$ then $\mathop {\lim }\limits_{n \to \infty } {x_n}$ is equal to
The value of $k$ for which the lines $7x - 8y + 5 = 0$, $3x - 4y + 5 = 0$ and $4x + 5y + k = 0$ are concurrent is given by
Choose the correct answer. The point $(4, 1)$ undergoes the following two successive transformations:
Let $a, b$ be two real numbers such that $a b < 0$. If the complex number $\frac{1+ ai }{ b + i }$ is of unit modulus and $a+i b$ lies on the circle $|z-1|=|2 z|$, then a possible value of $\frac{1+[ a ]}{4 b }$, where $[ t ]$ is greatest integer function, is :
$A =\{x: x$ is a letter of attract $\}$,
$B=\{y: y$ is a letter of cataract $\}$, then :
If the coefficients of $x^7$ in $\left( ax ^2+\frac{1}{2 bx }\right)^{11}$ and $x ^{-7}$ in $\left(a x-\frac{1}{3 b x^2}\right)^{11}$ are equal, then
Suppose

$\operatorname{det}\left[\begin{array}{cc}\sum_{k=0}^n k & \sum_{k=0}^n{ }^n C_k k^2 \\ \sum_{k=0}^n{ }^n C_k k & \sum_{k=0}^n{ }^n C_k 3^k\end{array}\right]=0$, holds for some positive integer $n$. Then $\sum_{k=0}^n \frac{{ }^n C_k}{k+1}$ equals

If $\mathop {\lim }\limits_{n \to \infty } \frac{1}{{10 + {{\left( {2\cos x} \right)}^{2n}}}} = 0$ , then complete set of all possible values of $|sin\  x|$ is 
The range of the function $\text{f(x)}=\frac{\text{x}^2-\text{x}}{\text{x}^2+2\text{x}}$ is: