3 and 4 .Determinants and Matrices
hard

यदि रेखीय समीकरणों के निकाय

$7 x+11 y+\alpha z=13$

$5 x+4 y+7 z=\beta$

$175 x+194 y+57 z=361$

के अनंत हल है, तो $\alpha+\beta+2$ बराबर है

A

$4$

B

$3$

C

$5$

D

$6$

(JEE MAIN-2023)

Solution

Sol. $7 x+11 y+\alpha z=13$

$5 x+4 y+7 z=\beta$

$175 x+194 y+57 z=361$

$\text { (i) } \times 10+(\text { ii }) \times 21-(\text { iii) }$

$z (10 \alpha+147-57)=130+21 \beta-361$

$\therefore 10 \alpha+90=0$

$\alpha=-9$

$130-361+21 \beta=0$

$\beta=11$

$\alpha+\beta+2=4$

Standard 12
Mathematics

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