JEE Advanced · Mathematics · 18. Matrices
Let \(I=\left(\begin{array}{ll}1 & 0 \\ 0 & 1\end{array}\right)\) and \(P=\left(\begin{array}{ll}2 & 0 \\ 0 & 3\end{array}\right)\). Let \(Q=\left(\begin{array}{ll}\mathrm{x} & \mathrm{y} \\ \mathrm{z} & 4\end{array}\right)\) for some non-zero real numbers \(x, y\), and \(z\), for which there is \(2 \times 2\) matrix \(R\) with all entries being non-zero real numbers, such that \(Q R=R P\). Then which of the following statements is (are) TRUE?
- A The determinant of \(Q-2 I\) is zero
- B The determinant of \(\mathrm{Q}-6 I\) is 12
- C The determinant of \(Q-3 I\) is 15
- D \(y z=2\)
Answer & Solution
Correct Answer
(B) The determinant of \(\mathrm{Q}-6 I\) is 12
Step-by-step Solution
Detailed explanation
\(\begin{aligned}
& \mathrm{QR}=\mathrm{RP} \\
& P=\left(\begin{array}{ll}
2 & 0 \\
0 & 3
\end{array}\right) \quad Q=\left(\begin{array}{ll}
x & y \\
z & 4
\end{array}\right) \\
& \left(\begin{array}{ll}
x & y \\
z & 4
\end{array}\right)\left(\begin{array}{ll}
r_1 & r_2 \\
r_3 & r_4
\end{array}\right)=\left(\begin{array}{ll}
r_1 & r_2 \\
r_3 & r_4
\end{array}\right)\left(\begin{array}{ll}
2 & 0 \\
0 & 3
\end{array}\right) \\
& \left.\begin{array}{l}
\mathrm{xr}_1+\mathrm{yr}_3=2 \mathrm{r}_1 \\
\mathrm{zr}_1+4 \mathrm{r}_3=2 \mathrm{r}_3
\end{array}\right\} \rightarrow \frac{\mathrm{x}-2}{-\mathrm{y}}=\frac{\mathrm{r}_3}{\mathrm{r}_1}=\frac{\mathrm{z}}{-2}
\end{aligned}\)
\(2 x-4=y z\)
\(\left.\begin{array}{l}\mathrm{xr}_2+\mathrm{yr}_4=3 \mathrm{r}_2 \\ \mathrm{zr}_2+4 \mathrm{r}_4=3 \mathrm{r}_4\end{array}\right\} \rightarrow \frac{\mathrm{x}-3}{-\mathrm{y}}=\frac{\mathrm{r}_4}{\mathrm{r}_2}=-\mathrm{z} \quad\) \(\mathrm{x}-3=\mathrm{yz}\)
\(\Rightarrow 2 x-4=x-3\) \(\Rightarrow x=1 ~\&~ y z=-2\)
\(\begin{aligned}
& \Rightarrow \mathrm{Q}-\lambda \mathrm{I}=\left(\begin{array}{cc}
\mathrm{x}-\lambda & \mathrm{y} \\
\mathrm{z} & 4-\lambda
\end{array}\right) \\
& |\mathrm{Q}-\lambda \mathrm{I}|=(\lambda-\mathrm{x})(\lambda-4)-\mathrm{yz} \\
& =\lambda^2-(\mathrm{x}+4) \lambda+4 \mathrm{x}-\mathrm{yz} \\
& |\mathrm{Q}-\lambda \mathrm{I}|=\lambda^2-5 \lambda+6
\end{aligned}\)
Now verify the option
& \mathrm{QR}=\mathrm{RP} \\
& P=\left(\begin{array}{ll}
2 & 0 \\
0 & 3
\end{array}\right) \quad Q=\left(\begin{array}{ll}
x & y \\
z & 4
\end{array}\right) \\
& \left(\begin{array}{ll}
x & y \\
z & 4
\end{array}\right)\left(\begin{array}{ll}
r_1 & r_2 \\
r_3 & r_4
\end{array}\right)=\left(\begin{array}{ll}
r_1 & r_2 \\
r_3 & r_4
\end{array}\right)\left(\begin{array}{ll}
2 & 0 \\
0 & 3
\end{array}\right) \\
& \left.\begin{array}{l}
\mathrm{xr}_1+\mathrm{yr}_3=2 \mathrm{r}_1 \\
\mathrm{zr}_1+4 \mathrm{r}_3=2 \mathrm{r}_3
\end{array}\right\} \rightarrow \frac{\mathrm{x}-2}{-\mathrm{y}}=\frac{\mathrm{r}_3}{\mathrm{r}_1}=\frac{\mathrm{z}}{-2}
\end{aligned}\)
\(2 x-4=y z\)
\(\left.\begin{array}{l}\mathrm{xr}_2+\mathrm{yr}_4=3 \mathrm{r}_2 \\ \mathrm{zr}_2+4 \mathrm{r}_4=3 \mathrm{r}_4\end{array}\right\} \rightarrow \frac{\mathrm{x}-3}{-\mathrm{y}}=\frac{\mathrm{r}_4}{\mathrm{r}_2}=-\mathrm{z} \quad\) \(\mathrm{x}-3=\mathrm{yz}\)
\(\Rightarrow 2 x-4=x-3\) \(\Rightarrow x=1 ~\&~ y z=-2\)
\(\begin{aligned}
& \Rightarrow \mathrm{Q}-\lambda \mathrm{I}=\left(\begin{array}{cc}
\mathrm{x}-\lambda & \mathrm{y} \\
\mathrm{z} & 4-\lambda
\end{array}\right) \\
& |\mathrm{Q}-\lambda \mathrm{I}|=(\lambda-\mathrm{x})(\lambda-4)-\mathrm{yz} \\
& =\lambda^2-(\mathrm{x}+4) \lambda+4 \mathrm{x}-\mathrm{yz} \\
& |\mathrm{Q}-\lambda \mathrm{I}|=\lambda^2-5 \lambda+6
\end{aligned}\)
Now verify the option
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Mathematics
- Let , be a continuous function then, which of the following function(s), has(have) the values zero at some point in the interval, (0,1)?JEE Advanced 2017 Hard
- Let \(X\) and \(Y\) be two events such that \(P(X \mid Y)=\frac{1}{2}\), \(P(Y / X)=\frac{1}{3}\) and \(P(X \cap Y)=\frac{1}{6}\). Which of the following is (are) correct?JEE Advanced 2012 Medium
- Let and be positive real numbers. Suppose and are the lengths of the sides of a triangle opposite to its angles and respectively. If , then which of the following statements is/are TRUE?JEE Advanced 2020 Medium
- Let \(\omega=e^{i \pi / 3}\) and \(a, b, c, x, y, z\) be non-zero complex numbers such that \(a+b+c=x, a+b \omega+c \omega^2=y, a+b \omega^2+c \omega=z\).
Then, the value of \(\frac{|x|^2+|y|^2+|z|^2}{|a|^2+|b|^2+|c|^2}\) isJEE Advanced 2011 Hard - Consider boxes, where each box contains red balls and blue balls. Assume that all balls are distinct. In how many different ways can balls be chosen from these boxes so that from each box at least one red ball and one blue ball are chosen?JEE Advanced 2022 Hard
- Let \(\alpha, \beta\) and \(\gamma\) be real numbers such that the system of linear equations
\[
\begin{array}{c}
x+2 y+3 z=\alpha \\
4 x+5 y+6 z=\beta \\
7 x+8 y+9 z=\gamma-1
\end{array}
\]
is consistent. Let \(|M|\) represent the determinant of the matrix
\[
M=\left[\begin{array}{ccc}
\alpha & 2 & \gamma \\
\beta & 1 & 0 \\
-1 & 0 & 1
\end{array}\right]
\]
Let \(P\) be the plane containing all those \((\alpha, \beta, \gamma)\) for which the above system of linear equations is consistent, and \(D\) be the square of the distance of the point \((0,1,0)\) from the plane \(P\).
The value of isJEE Advanced 2021 Medium
More PYQs from JEE Advanced
- The standard reduction potential data at is given below.
\(E ^o\left( Fe ^{3+}, Fe ^{2+}\right)=+0.77 V ; \)
\( E ^o\left( Fe ^{2+}, Fe \right)=-0 . 44 V \)
\( E ^o\left( Cu ^{2+}, Cu \right)=+0.34 V ; \)
\( E ^o\left( Cu ^{+}, Cu \right)=+0.52 V \)
\( E ^o\left[ O _2(g)+4 H ^{+}+4 e ^{-} \rightarrow 2 H _2 O \right]=\) \(+1.23~V \)
\( E ^o\left[ O _2(g)+2 H _2 O +4 e^{-} \longrightarrow \text { 4OH}^{-}\right]=\) \(+0.40~V \)
\( E ^o\left( Cr ^{3+}, Cr \right)=-0.74 V ; \)
\( E ^o\left( Cr ^{2+}, Cr \right)=-0.91 V\)
Match Eo of the redox pair in List I with the values given in List II and select the correct answer using the code given below the lists :
List I List II A. P. B. Q. C R. D. S. JEE Advanced 2013 Hard - Let \(f:(0,1) \rightarrow R\) be defined by \(f(x)=\frac{b-x}{1-b x}\), where \(b\) is a constant such that \(0 < b < 1\). Then,JEE Advanced 2011 Hard
- The binding energy of nucleons in a nucleus can be affected by the pairwise Coulomb repulsion. Assume that all nucleons are uniformly distributed inside the nucleus. Let the binding energy of a proton be and the binding energy of a neutron be in the nucleus.
Which of the following statement(s) is(are) correct?JEE Advanced 2022 Medium - Let and . Then which of the following statements is(are) true?JEE Advanced 2023 Hard
- Match the gases under specified conditions listed in Column I with their properties/laws in Column II. Indicate your answer by darkening the appropriate bubbles of \(4 \times 4\) matrix given in the ORS.
Column I Column II A. Hydrogen gas
\((P=200 atm,\) \(T=273 K)\)p. Compressibility factor \(\neq 1\) B. Hydrogen gas
\((P \sim 0,\) \(T=273 K)\)q. Attractive forces are dominant C. \(CO _2(P=1 atm,\) \(T=273 K)\) r. \(P V=n R T\) D. Real gas with very large molar volume s. \(P(V-n b)=n R T\) JEE Advanced 2007 Medium - The coefficients of three consecutive terms of are in the ratio . ThenJEE Advanced 2013 Easy