Medium MCQ +4 / -1 PYQ · JEE Mains 2020

If $\alpha$ and $\beta$ be two roots of the equation
x2 – 64x + 256 = 0. Then the value of
$${\left( {{{{\alpha ^3}} \over {{\beta ^5}}}} \right)^{1/8}} + {\left( {{{{\beta ^3}} \over {{\alpha ^5}}}} \right)^{1/8}}$$ is :

  1. A 1
  2. B 3
  3. C 2 Correct answer
  4. D 4

Solution

x<sup>2</sup> – 64x + 256 = 0 <br><br>$\alpha$ + $\beta$ = 64, $\alpha$$\beta$ = 256 <br><br>$${\left( {{{{\alpha ^3}} \over {{\beta ^5}}}} \right)^{1/8}} + {\left( {{{{\beta ^3}} \over {{\alpha ^5}}}} \right)^{1/8}}$$ <br><br>= $${{{\alpha ^{{3 \over 8}}}} \over {{\beta ^{{5 \over 8}}}}} + {{{\beta ^{{3 \over 8}}}} \over {{\alpha ^{{5 \over 8}}}}}$$ <br><br>= ${{\alpha + \beta } \over {{{\left( {\alpha \beta } \right)}^{{5 \over 8}}}}}$ <br><br>= ${{64} \over {{{\left( {256} \right)}^{{5 \over 8}}}}}$ <br><br>= 2

About this question

Subject: Mathematics · Chapter: Complex Numbers and Quadratic Equations · Topic: Complex Numbers and Argand Plane

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