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QJEEM22Mad1d7: JEE Main 2022 Mathematics - Class 11 JEEM22Mad1d7 Solution: Let for some real numbers and , . If the system of equations…

Let for some real numbers α\alpha and β\beta , a=α−iβa = \alpha - i\beta . If the system of equations 4ix+(1+i)y=04ix + (1 + i)y = 0 and 8(cos⁡2π3+isin⁡2π3)x+a‾y=08\left( {\cos {{2\pi } \over 3} + i\sin {{2\pi } \over 3}} \right)x + \overline a y = 0 has more than one solution, then αβ{\alpha \over \beta } is equal to

Multiple Choice Options

  • A −23- 2\sqrt 3
  • B 2−32 - \sqrt 3
  • C 2+32 + \sqrt 3
  • D −2−3- 2 - \sqrt 3

Step-by-Step Verified Solution

Given a=α−iβa = \alpha - i\beta and

4ix+(1+i)y=04ix + (1 + i)y = 0 ...... (i)

8(cos⁡2π3+isin⁡2π3)x+a‾y=08\left( {\cos {{2\pi } \over 3} + i\sin {{2\pi } \over 3}} \right)x + \overline a y = 0 .... (ii)

By (i)

xy=−(1+i)4i{x \over y} = {{ - (1 + i)} \over {4i}} ...... (iii)

By (ii)

xy=−a‾8(−12+3i2){x \over y} = {{ - \overline a } \over {8\left( {{{ - 1} \over 2} + {{\sqrt 3 i} \over 2}} \right)}} ..... (iv)

Now by (iii) and (iv)

1+i4i=a‾4(−1+3i){{1 + i} \over {4i}} = {{\overline a } \over {4\left( { - 1 + \sqrt 3 i} \right)}}

⇒a‾=(3−1)+(3+1)i\Rightarrow \overline a = \left( {\sqrt 3 - 1} \right) + \left( {\sqrt 3 + 1} \right)i

⇒α+iβ=(3−1)+(3+1)i\Rightarrow \alpha + i\beta = \left( {\sqrt 3 - 1} \right) + \left( {\sqrt 3 + 1} \right)i

∴\therefore αβ=3−13+1=2−3{\alpha \over \beta } = {{\sqrt 3 - 1} \over {\sqrt 3 + 1}} = 2 - \sqrt 3

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