3 and 4 .Determinants and Matrices
hard

The greatest value of $c \in R$ for which the system of linear equations

$x - cy - cz = 0 \,\,;\,\, cx - y + cz = 0 \,\,;\,\, cx + cy - z = 0 $ has a non -trivial solution, is

A

$-1$

B

$0.5$

C

$2$

D

$0$

(JEE MAIN-2019)

Solution

For non -trivial solution

$D = 0$

$\left| {\begin{array}{*{20}{c}}
1&{ – c}&{ – c}\\
c&{ – 1}&c\\
c&c&{ – 1}
\end{array}} \right| = 0 \Rightarrow 2{c^3} + 3{c^2} – 1 = 0$

$ \Rightarrow {\left( {c + 1} \right)^2}\left( {2c – 1} \right) = 0$ 

$\therefore $ Greatest value of $c$ is $\frac{1}{2}$

Standard 12
Mathematics

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