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3 and 4 .Determinants and Matrices
normal
If $a\, -\, 2b + c = 1$ , then value of $\left| {\begin{array}{*{20}{c}}
{x + 1}&{x + 2}&{x + a} \\
{x + 2}&{x + 3}&{x + b} \\
{x + 3}&{x + 4}&{x + c}
\end{array}} \right|$ is
A
$x$
B
$-x$
C
$-1$
D
$1$
Solution
$\mathrm{R}_{1} \rightarrow \mathrm{R}_{1}-2 \mathrm{R}_{2}+\mathrm{R}_{3}$
$\left|\begin{array}{ccc}{0} & {0} & {1} \\ {\mathrm{x}+2} & {\mathrm{x}+3} & {\mathrm{x}+\mathrm{b}} \\ {\mathrm{x}+3} & {\mathrm{x}+4} & {\mathrm{x}+\mathrm{c}}\end{array}\right|$
$\mathrm{R}_{3} \rightarrow \mathrm{R}_{3}-\mathrm{R}_{2} \Rightarrow \Delta=-1$
Standard 12
Mathematics