All Exams Test series for 1 year @ ₹349 only
Question

Let $x$ and $y$ be real numbers such that $50\left(\frac{2x}{1+3i} - \frac{y}{1-2i}\right) = 31 + 17i$, $i = \sqrt{-1}$. Then the value of $10(x-3y)$ is :

The correct answer is
75

Solving Complex Number Equation

We are given the equation: $50\left(\frac{2x}{1+3i} - \frac{y}{1-2i}\right) = 31 + 17i$ We need to find the value of $10(x-3y)$. $x$ and $y$ are real numbers.

Step 1: Simplify Complex Fractions

First, rationalize the denominators:

  • $\frac{2x}{1+3i} = \frac{2x(1-3i)}{(1+3i)(1-3i)} = \frac{2x(1-3i)}{1^2 + 3^2} = \frac{2x(1-3i)}{10} = \frac{x(1-3i)}{5}$
  • $\frac{y}{1-2i} = \frac{y(1+2i)}{(1-2i)(1+2i)} = \frac{y(1+2i)}{1^2 + 2^2} = \frac{y(1+2i)}{5}$

Step 2: Substitute and Simplify the Equation

Substitute the simplified fractions back into the main equation:

$50\left(\frac{x(1-3i)}{5} - \frac{y(1+2i)}{5}\right) = 31 + 17i$ $10\left( x(1-3i) - y(1+2i) \right) = 31 + 17i$ $10\left( x - 3xi - y - 2yi \right) = 31 + 17i$

Group the real and imaginary terms:

$10\left( (x-y) - (3x+2y)i \right) = 31 + 17i$ $(10x - 10y) - (30x + 20y)i = 31 + 17i$

Step 3: Equate Real and Imaginary Parts

Equate the real parts and the imaginary parts of the equation:

  • Real part: $10x - 10y = 31$ (Equation 1)
  • Imaginary part: $-(30x + 20y) = 17 \implies 30x + 20y = -17$ (Equation 2)

Step 4: Solve the System of Linear Equations

Solve the system formed by Equation 1 and Equation 2:

  1. Multiply Equation 1 by 3: $30x - 30y = 93$ (Equation 3)
  2. Subtract Equation 2 from Equation 3: $(30x - 30y) - (30x + 20y) = 93 - (-17)$ $-50y = 110$ $y = -\frac{110}{50} = -\frac{11}{5}$
  3. Substitute $y = -\frac{11}{5}$ into Equation 1: $10x - 10\left(-\frac{11}{5}\right) = 31$ $10x + 22 = 31$ $10x = 9$ $x = \frac{9}{10}$

Step 5: Calculate the Target Expression

Calculate the value of $10(x-3y)$ using the found values of $x$ and $y$:

$10(x-3y) = 10\left(\frac{9}{10} - 3\left(-\frac{11}{5}\right)\right)$ $10\left(\frac{9}{10} + \frac{33}{5}\right)$ $10\left(\frac{9}{10} + \frac{66}{10}\right)$ $10\left(\frac{9 + 66}{10}\right)$ $10\left(\frac{75}{10}\right)$ $10(x-3y) = 75$
Was this answer helpful?

Similar Questions

  1. Let A = {-3, -2, -1, 0, 1, 2, 3}. Let R be a relation on A defined by xRy if and only if $0\le x^2+2y\le 4$. Let $l$ be the number of elements in R and $m$ be the minimum number of elements required to be added in R to make it a reflexive relation. Then $l + m$ is equal to

  2. Let $\alpha$ and $\beta$ be the roots of $x^2 + \sqrt{3}x-16=0$, and $\gamma$ and $\delta$ be the roots of $x^2 + 3x - 1 = 0$. If $P_n = \alpha^n + \beta^n$ and $Q_n = \gamma^n + \delta^n$, then $\frac{P_{25} + \sqrt{3}P_{24}}{2P_{23}} + \frac{Q_{25}-Q_{23}}{Q_{24}}$ is equal to

  3. Let the domain of the function $f (x) = \log_2 \log_4 \log_6(3 + 4x -x^2)$ be $(a, b)$. 

    If  $\int_{b-a}^{b+a}[x^2] dx=p-\sqrt{q}-\sqrt{r}$, $p,q,r\in N$, $gcd(p,q,r) = 1$, where $[.]$ is the greatest integer function, then $p + q + r$ is equal to

  4. Let A be a matrix of order $3 \times 3$ and $|A| = 5$. If $|2\text{adj} (3A \text{adj} (2A))| = 2^\alpha \cdot 3^\beta \cdot 5^\gamma$, $\alpha, \beta, \gamma \in N$, then $\alpha + \beta + \gamma$ is equal to

  5. Let $a_1, a_2, a_3,....$ be a G.P. of increasing positive numbers. If $a_3a_5 = 729$ and $a_2 + a_4 = \frac{111}{4}$, then $24 (a_1 + a_2 + a_3)$ is equal to

  6. All five letter words are made using all the letters A, B, C, D, E and arranged as in an English dictionary with serial numbers. Let the word at serial number $n$ be denoted by $W_n$. Let the probability $P(W_n)$ of choosing the word $W_n$ satisfy $P(W_n) = 2P(W_{n-1})$, $n > 1$.

     If $P(CDBEA) = \frac{2^\alpha}{2^\beta-1}$, $\alpha, \beta\in N$, then $\alpha + \beta$ is equal to :

  7. The largest $n \in N$ such that $3^n$ divides $50!$ is :
  8. The number of sequences of ten terms, whose terms are either 0 or 1 or 2, that contain exactly five 1s and exactly three 2s, is equal to :
  9. Let A be the set of all functions $f: Z \to Z$ and R be a relation on A such that $R = \{(f, g) : f(0) = g(1) \text{ and } f(1) = g(0)\}$. Then R is :
  10. Let $a \in \mathbf{R}$ and $A$ be a matrix of order $3 \times 3$ such that $\det (A) = -4$ and $A + I = \begin{bmatrix} 1 & a & 1 \\ 2 & 1 & 0 \\ a & 1 & 2 \end{bmatrix}$, where $I$ is the identity matrix of order $3 \times 3$. If $\det ((a+1)\text{adj}((a-1)A))$ is $2^m 3^n$, $m, n \in \{0, 1, 2, \dots, 20\}$, then $m+n$ is equal to :


Important Questions from Algebra

  1. Let A = {-3, -2, -1, 0, 1, 2, 3}. Let R be a relation on A defined by xRy if and only if $0\le x^2+2y\le 4$. Let $l$ be the number of elements in R and $m$ be the minimum number of elements required to be added in R to make it a reflexive relation. Then $l + m$ is equal to

  2. Let $\alpha$ and $\beta$ be the roots of $x^2 + \sqrt{3}x-16=0$, and $\gamma$ and $\delta$ be the roots of $x^2 + 3x - 1 = 0$. If $P_n = \alpha^n + \beta^n$ and $Q_n = \gamma^n + \delta^n$, then $\frac{P_{25} + \sqrt{3}P_{24}}{2P_{23}} + \frac{Q_{25}-Q_{23}}{Q_{24}}$ is equal to

  3. Let the domain of the function $f (x) = \log_2 \log_4 \log_6(3 + 4x -x^2)$ be $(a, b)$. 

    If  $\int_{b-a}^{b+a}[x^2] dx=p-\sqrt{q}-\sqrt{r}$, $p,q,r\in N$, $gcd(p,q,r) = 1$, where $[.]$ is the greatest integer function, then $p + q + r$ is equal to

  4. Let A be a matrix of order $3 \times 3$ and $|A| = 5$. If $|2\text{adj} (3A \text{adj} (2A))| = 2^\alpha \cdot 3^\beta \cdot 5^\gamma$, $\alpha, \beta, \gamma \in N$, then $\alpha + \beta + \gamma$ is equal to

  5. Let $a_1, a_2, a_3,....$ be a G.P. of increasing positive numbers. If $a_3a_5 = 729$ and $a_2 + a_4 = \frac{111}{4}$, then $24 (a_1 + a_2 + a_3)$ is equal to

Need Expert Advice?
More Questions from JEE Main

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App