A) \[3\]
B) \[9\]
C) \[6\]
D) \[2\sqrt{7}\]
Correct Answer: C
Solution :
Key Idea: For the ellipse\[\frac{{{x}^{2}}}{{{a}^{2}}}+\frac{{{y}^{2}}}{{{b}^{2}}}=1\] the length of major axis \[=2a\], if \[a>b\] and major axis is \[2b\], if\[a<b\]. Given equation of ellipse\[9{{x}^{2}}+7{{y}^{2}}=63\] \[\Rightarrow \] \[\frac{{{x}^{2}}}{7}+\frac{{{y}^{2}}}{9}=1\] \[{{a}^{2}}=7,{{b}^{2}}=9\] Since, \[a<b\] \[\Rightarrow \]Length of major axis\[=2b=6\]
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