Three numbers are in an increasing geometric progression with common ratio $\mathrm{r}$. If the middle number is doubled, then the new numbers are in an arithmetic progression with common difference $\mathrm{d}$. If the fourth term of GP is $3 \mathrm{r}^{2}$, then $\mathrm{r}^{2}-\mathrm{d}$ is equal to:
$7-7 \sqrt{3}$
$7+\sqrt{3}$
$7-\sqrt{3}$
$7+3 \sqrt{3}$
If $a,\;b,\;c$ are in $A.P.$ and $a,\;b,\;d$ in $G.P.$, then $a,\;a - b,\;d - c$ will be in
If $x\in (0,\frac{\pi}{4})$ then the expression $ \frac{cos x}{sin^2 x(cos x-sin x)}$ can not take the value
The geometric and harmonic means of two numbers $x_1$ and $x_2$ are $18$ and $16\frac {8}{13}$ respectively. The value of $|x_1 -x_2|$ is
Suppose $a,\,b,\,c$ are in $A.P.$ and ${a^2},{b^2},{c^2}$ are in $G.P.$ If $a < b < c$ and $a + b + c = \frac{3}{2}$, then the value of $a$ is
If $A.M.$ of two terms is $9$ and $H.M.$ is $36$, then $G.M.$ will be