3 and 4 .Determinants and Matrices
hard

$\left| {\,\begin{array}{*{20}{c}}{{a^2} + {x^2}}&{ab}&{ca}\\{ab}&{{b^2} + {x^2}}&{bc}\\{ca}&{bc}&{{c^2} + {x^2}}\end{array}\,} \right|$ का भाजक है  

A

${a^2}$

B

${b^2}$

C

${c^2}$

D

${x^2}$

Solution

(d) $\left| {\,\begin{array}{*{20}{c}}{{a^2} + {x^2}}&{ab}&{ca}\\{ab}&{{b^2} + {x^2}}&{bc}\\{ca}&{bc}&{{c^2} + {x^2}}\end{array}\,} \right|$

${C_1},\,{C_2},{C_3}$ को क्रमश: $a,\,\,b,\,c$ से गुणा तथा $ abc$  से भाग देने पर,

 $\Delta = \frac{1}{{abc}}\,\left| {\,\begin{array}{*{20}{c}}{a({a^2} + {x^2})}&{a{b^2}}&{{c^2}a}\\{{a^2}b}&{b({b^2} + {x^2})}&{b{c^2}}\\{c{a^2}}&{{b^2}c}&{c({c^2} + {x^2})}\end{array}\,} \right|$

अब ${R_1},\,{R_2}$ और ${R_3}$ से क्रमश: $a, b , c $  उभयनिष्ठ निकालने पर,

 $\Delta = \left| {\,\begin{array}{*{20}{c}}{{a^2} + {x^2}}&{{b^2}}&{{c^2}}\\{{a^2}}&{{b^2} + {x^2}}&{{c^2}}\\{{a^2}}&{{b^2}}&{{c^2} + {x^2}}\end{array}\,} \right|$

अब ${C_1} \to {C_1} + {C_2} + {C_3}$ के द्वारा

$ \Rightarrow $ $\Delta = ({a^2} + {b^2} + {c^2} + {x^2})\,\left| {\,\begin{array}{*{20}{c}}1&{{b^2}}&{{c^2}}\\1&{{b^2} + {x^2}}&{{c^2}}\\1&{{b^2}}&{{c^2} + {x^2}}\end{array}\,} \right|$

==> $\Delta = {x^4}({a^2} + {b^2} + {c^2} + {x^2})$

अत:, ${x^2}$ से विभाज्य है।

Standard 12
Mathematics

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