જો $\left| {\,\begin{array}{*{20}{c}}{x + 1}&{x + 2}&{x + 3}\\{x + 2}&{x + 3}&{x + 4}\\{x + a}&{x + b}&{x + c}\end{array}\,} \right| = 0$, તો $a,b,c$ એ . . . શ્રેણીમાં છે.
A
સમાંતર
B
સમગુણોતર
C
સ્વરિત
D
એકપણ નહી.
Medium
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A
સમાંતર
As given $\left| {\,\begin{array}{*{20}{c}}{x + 1}&{x + 2}&{x + 3}\\{x + 2}&{x + 3}&{x + 4}\\{x + a}&{x + b}&{x + c}\end{array}\,} \right|\, = \,0$
= $\left| {\,\begin{array}{*{20}{c}}{ - 1}&{ - 1}&{x + 3}\\{ - 1}&{ - 1}&{x + 4}\\{a - b}&{b - c}&{x + c}\end{array}\,} \right|\, = 0$,
by $\begin{array}{l}{C_1} \to {C_1} - {C_2}\\{C_2} \to {C_2} - {C_3}\end{array}$
$ \Rightarrow $ $\left| {\,\begin{array}{*{20}{c}}0&0&{ - 1}\\{ - 1}&{ - 1}&{x + 4}\\{a - b}&{b - c}&{x + c}\end{array}\,} \right|\, = 0$, by ${R_1} \to {R_1} - {R_2}$
$ \Rightarrow $$( - 1)\,( - b + c + a - b)\, = 0$
$ \Rightarrow $ $2b - a - c = 0 \Rightarrow a + c = 2b$ i.e., $a,b,c$ are in $A.P.$ Trick : In such type of problem, put any suitable value of $x$ i.e. $0$, so that the determinant.
$\left| {\,\begin{array}{*{20}{c}}1&2&3\\2&3&4\\a&b&c\end{array}\,} \right| = 0$
$ \Rightarrow 1\,(3c - 4b) - 2(2c - 4a) + 3(2b - 3a) = 0$
$ \Rightarrow $ $ - c + 2b - a = 0 \Rightarrow 2b = a + c$. Hence the result.
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જો $\Delta = \left| {\,\begin{array}{*{20}{c}}a&b&c\\x&y&z\\p&q&r\end{array}\,} \right|$, તો $\left| {\,\begin{array}{*{20}{c}}{ka}&{kb}&{kc}\\{kx}&{ky}&{kz}\\{kp}&{kq}&{kr}\end{array}\,} \right|$=
અહી $P$ એ ચોરસ શ્રેણિક છે કે જેથી $P ^2= I - P$ થાય. $\alpha, \beta, \gamma, \delta \in N$ માટે જો $P ^\alpha+ P ^\beta=\gamma I -29 P$ અને $P ^\alpha- P ^\beta=$ $\delta I-13 P$ હોય તો $\alpha+\beta+\gamma-\delta$ ની કિમંત મેળવો.
$\alpha, \beta \in R$ માટે, ધારો કે સુરેખ સમીકરણ સંહતિ $x-y+z=5$ ; $2 x+2 y+\alpha z=8$ ; $3 x-y+4 z=\beta$ ને અસંખ્ય ઉકેલો છે. તો $\alpha$ અને $\beta$ એ $........$ ના બીજ છે.