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8. Sequences and Series
easy
$x$ ની કઈ કિંમત માટે $\frac{2}{7}, x,-\frac{7}{2}$ સમગુણોત્તર શ્રેણીમાં થાય ?
A
$\pm 1$
B
$\pm 1$
C
$\pm 1$
D
$\pm 1$
Solution
The given numbers are $\frac{-2}{7}, x, \frac{-7}{2}$
Common ratio $=\frac{x}{-2 / 7}=\frac{-7 x}{2}$
Also, common ratio $=\frac{-7 / 2}{x}=\frac{-7}{2 x}$
$\therefore \frac{-7 x}{2}=\frac{-7}{2 x}$
$\Rightarrow x^{2}=\frac{-2 \times 7}{-2 \times 7}=1$
$\Rightarrow x=\sqrt{1}$
$\Rightarrow x=\pm 1$
Thus, for $x=\pm 1,$ the given numbers will be in $G.P.$
Standard 11
Mathematics
