If ${a^2},\,{b^2},\,{c^2}$ be in $A.P.$, then $\frac{a}{{b + c}},\,\frac{b}{{c + a}},\,\frac{c}{{a + b}}$ will be in
$A.P.$
$G.P.$
$H.P.$
None of these
The first term of an $A.P. $ is $2$ and common difference is $4$. The sum of its $40$ terms will be
If the sum of $n$ terms of an $A.P.$ is $nA + {n^2}B$, where $A,B$ are constants, then its common difference will be
If three numbers be in $G.P.$, then their logarithms will be in
The ratio of the sums of $m$ and $n$ terms of an $A.P.$ is $m^{2}: n^{2} .$ Show that the ratio of $m^{ th }$ and $n^{ th }$ term is $(2 m-1):(2 n-1)$
Write the first five terms of the sequences whose $n^{t h}$ term is $a_{n}=n(n+2)$