The value of $$\frac{1}{2}\left(\frac{1}{5}\right)^2+\frac{2}{3}\left(\frac{1}{5}\right)^3+\frac{3}{4}\left(\frac{1}{5}\right)^4+\ldots . . \infty$$ is

If the real numbers $$x, y, z, t$$ be in GP then the value of $$(x^2+y^2+z^2)(y^2+z^2+t^2)$$ is euqal to

The value of $$\frac{4}{1 !}+\frac{11}{2 !}+\frac{22}{3 !}+\frac{37}{4 !}+\frac{56}{5 !}+\ldots \infty$$ is