Cunning Complex 6

Algebra Level 4

Find the sum of real values of x x and y y for which the following equation is satisfied:

( 1 + i ) x 2 i 3 + i + ( 2 3 i ) y + i 3 i = i . \frac { \left( 1+i \right) x-2i }{ 3+i } + \frac { \left( 2-3i \right) y+i }{ 3-i } =i.

This problem is part of a set .


The answer is 2.00.

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4 solutions

Ojna Eugitaraba
Mar 27, 2015

L H S = ( 1 + i ) x 2 i 3 + i + ( 2 3 i ) y + i 3 i LHS = \displaystyle\frac{{(1 + i)x - 2i}}{{3 + i}} + \displaystyle\frac{{(2 - 3i)y + i}}{{3 - i}}

= [ ( 1 + i ) x 2 i ] ( 3 i ) 10 + [ ( 2 3 i ) y + i ] ( 3 i ) 10 = \displaystyle\frac{{\left[ {(1 + i)x - 2i} \right](3 - i)}}{{10}} + \displaystyle\frac{{\left[ {(2 - 3i)y + i} \right](3 - i)}}{{10}}

= 2 5 x + i x 5 1 5 3 i 5 + 3 i 10 7 y i 10 + 9 y 10 1 10 = \displaystyle\frac{2}{5}x + \displaystyle\frac{{ix}}{5} - \displaystyle\frac{1}{5} - \displaystyle\frac{{3i}}{5} + \displaystyle\frac{{3i}}{{10}} - \displaystyle\frac{{7yi}}{{10}} + \displaystyle\frac{{9y}}{{10}} - \displaystyle\frac{1}{{10}}

= i ( x 5 7 y 10 3 10 ) + ( 2 x 5 + 9 y 10 3 10 ) = 1 i + 0 = i\left( {\displaystyle\frac{x}{5} - \displaystyle\frac{{7y}}{{10}} - \displaystyle\frac{3}{{10}}} \right) + \left( {\displaystyle\frac{{2x}}{5} + \displaystyle\frac{{9y}}{{10}} - \displaystyle\frac{3}{{10}}} \right) = 1i+0

As two complex numbers are equal if and only if their real parts are equal and their imaginary parts are also equal, we have:

{ x 5 7 y 10 3 10 = 1 2 x 5 + 9 y 10 3 10 = 0 \left\{ \begin{array}{l} \displaystyle\frac{x}{5} - \displaystyle\frac{{7y}}{{10}} - \displaystyle\frac{3}{{10}} = 1 \\ \displaystyle\frac{{2x}}{5} + \displaystyle\frac{{9y}}{{10}} - \displaystyle\frac{3}{{10}} = 0 \\ \end{array} \right.

{ x = 3 y = 1 \Leftrightarrow \left\{ \begin{array}{l} x = 3 \\ y = - 1 \\ \end{array} \right.

Hence, the sum of real values of x , y x,y is 2 \boxed{2}

@ Tín Phạm Nguyễn Nice solution for a really overrated problem

Utkarsh Bansal - 6 years, 2 months ago

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I can't imagine this problem being worth 400 points!

Tín Phạm Nguyễn - 6 years, 2 months ago
Terrell Bombb
Oct 6, 2016

Mayank Singh
Mar 18, 2015

Is there a better solution other than putting x=a+ib and so for y...

see my above solution.. hope you will like it :D

Ojna Eugitaraba - 6 years, 2 months ago

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That's same as putting a+ib

Mayank Singh - 6 years, 2 months ago

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