Question : If $m-n=2$ and $mn=15,(m,n>0)$ , then the value of $(m^2-n^2)(m^3-n^3)$ is:

Question : If $l+m+n=9$ and $l^{2}+m^{2}+n^{2}=31$, then the value of $(lm+mn+nl )$ will be:

Question : If $x^{4}+2x^{3}+ax^{2}+bx+9$ is a perfect square, where a and b are positive real numbers, then the value of $a$ and $b$ are:

Question : If $x$,$y$ and $z$ are real numbers such that $(x-3)^2+(y-4)^2+(z-5)^2=0$, then $(x+y+z)$ is equal to:

Question : If $\frac{\cos\alpha}{\cos\beta}= m$ and $\frac{\cos\alpha}{\sin\beta}= n$, then the value of $(m^{2}+n^{2})\cos^{2}\beta$ is: