KCET · Maths · Determinants
If \(A=\left|\begin{array}{lll}x & 1 & 1 \\ 1 & x & 1 \\ 1 & 1 & x\end{array}\right|\) and \(B=\left|\begin{array}{cc}x & 1 \\ 1 & x\end{array}\right|\), then \(\frac{d A}{d x}\) is equal to
- A \(3 B+1\)
- B \(3 B\)
- C \(-3 B\)
- D \(1-3 B\)
Answer & Solution
Correct Answer
(B) \(3 B\)
Step-by-step Solution
Detailed explanation
\(\begin{array}{ll}
\text { Given, } & A=\left|\begin{array}{lll}
x & 1 & 1 \\
1 & x & 1 \\
1 & 1 & x
\end{array}\right| \\
\Rightarrow & A=x\left(x^{2}-1\right)-(x-1)+(1-x) \\
\Rightarrow & A=x^{3}-x-x+1+1-x \\
\Rightarrow & A=x^{3}-3 x+2
\end{array}\)
On differentiating w.r.t. \(x\), we get
\(\frac{d A}{d x}=3 x^{2}-3..(i)\)
Also, given \(\quad B=\left|\begin{array}{ll}x & 1 \\ 1 & x\end{array}\right|\)
\(\begin{array}{cc}
\Rightarrow & B=x^{2}-1 \\
\Rightarrow & 3 B=3 x^{2}-3...(ii)
\end{array}\)
From Eqs. (i) and (ii), we get
\(\frac{d A}{d x}=3 B\)
\text { Given, } & A=\left|\begin{array}{lll}
x & 1 & 1 \\
1 & x & 1 \\
1 & 1 & x
\end{array}\right| \\
\Rightarrow & A=x\left(x^{2}-1\right)-(x-1)+(1-x) \\
\Rightarrow & A=x^{3}-x-x+1+1-x \\
\Rightarrow & A=x^{3}-3 x+2
\end{array}\)
On differentiating w.r.t. \(x\), we get
\(\frac{d A}{d x}=3 x^{2}-3..(i)\)
Also, given \(\quad B=\left|\begin{array}{ll}x & 1 \\ 1 & x\end{array}\right|\)
\(\begin{array}{cc}
\Rightarrow & B=x^{2}-1 \\
\Rightarrow & 3 B=3 x^{2}-3...(ii)
\end{array}\)
From Eqs. (i) and (ii), we get
\(\frac{d A}{d x}=3 B\)
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 Maths
- Domain of the function \(f\), given by \(f(x)=\frac{1}{\sqrt{(x-2)(x-5)}}\) isKCET 2025 Easy
- The value of \(\int e^{\sin x} \sin 2 x d x\) isKCET 2020 Medium
- On the set of positive rationals, a binary operation * is defined by \( a^{*} b=\frac{2 a b}{5} \). If \( 2^{*} x=3^{-1} \)
then \( x= \)KCET 2019 Easy - If the volume of the parallelopiped formed by three non-coplanar vectors \(\mathbf{a}, \mathbf{b}\) and \(\mathbf{c}\) is 4 cu units, then \([\mathbf{a} \times \mathbf{b} \mathbf{b} \times \mathbf{c} \mathbf{c} \times \mathbf{a}]\) is equal toKCET 2012 Medium
- If \(\alpha, \beta\) and \(\gamma\) are the roots of the equation \(x^{3}+4 x+2=0\), then \(\alpha^{3}+\beta^{3}+\gamma^{3}\) is equal toKCET 2012 Easy
- The total number of common tangents of \(x^{2}+y^{2}-6 x-8 y+9=0\) and \(x^{2}+y^{2}=1\) isKCET 2011 Easy
More PYQs from KCET
- The property which is not true about Fluorine is,KCET 2016 Easy
- The correct order for wavelengths of light absorbed in the complex ions \(\left[\operatorname{CoCl}\left(\mathrm{NH}_{3}\right)_{5}\right]^{2+},\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}\) and \(\left[\mathrm{Co}(\mathrm{CN})_{6}\right]^{3-}\) isKCET 2021 Medium
- If the function \( g(x) \) is defined by
\[
g(x)=\frac{\chi^{200}}{200}+\frac{\chi^{199}}{199}+\frac{\chi^{198}}{198}+\ldots \ldots+\frac{\chi^{2}}{2}+\chi+5, \text { then } g^{\prime}(0)=
\]KCET 2015 Easy - Match List-I with List-II
\begin{array}{|l|l|l|l|}\hline & \text{List-I (Types of redox reactions)} & & \text{List-II (Examples)} \\\hline \text{a}. & \text{Combination reaction} & \text{(i)} & \mathrm{Cl}_{2(\mathrm{~g})}+2 \mathrm{Br}_{(\mathrm{aq})}^{-} \rightarrow 2 \mathrm{Cl}_{(\mathrm{aq})}^{-}+\mathrm{Br}_{2(\mathrm{l})} \\\hline \text{b.} & \text{Decomposition reaction} & \text{(ii)} & 2 \mathrm{H}_2 \mathrm{O}_{2(\mathrm{aq})} \rightarrow 2 \mathrm{H}_2 \mathrm{O}_{(1)}+\mathrm{O}_{2(\mathrm{~g})} \\\hline \text{c.} & \text{Displacement reaction} & \text{(iii)} & \mathrm{CH}_{4(\mathrm{~g})}+2 \mathrm{O}_{2(\mathrm{~g})} \xrightarrow{\Delta} \mathrm{CO}_{2(\mathrm{~g})}+2 \mathrm{H}_2 \mathrm{O}_{(1)} \\\hline \text{d.} & \text{Disproportionation reaction} & \text{(iv)} & \mathrm{H}_2 \mathrm{O}_{(1)} \xrightarrow{\Delta} 2 \mathrm{H}_{2(\mathrm{~g})}+\mathrm{O}_{2(\mathrm{~g})} \\\hline\end{array}
Choose the correct answer from the options given below.KCET 2025 Medium - The angles \(A, B\) and \(C\) of a triangle \(A B C\) are in AP. If \(\mathrm{b}: \mathrm{c}=\sqrt{3}: \sqrt{2}\), then the angle \(\mathrm{A}\) isKCET 2008 Medium
- Which of the following monomers can undergo condensation polymerisation?KCET 2020 Easy