If x^2 + 1x^2 = 98 , ( x > 0 ) , then the value of x^3 + 1x^3 is?

Answer: Option A

$$\begin{array}{rl}& x^2+\frac{1}{x^2}=98\\ & \Rightarrow x^2+\frac{1}{x^2}+2=100\\ & \Rightarrow {\left(x+\frac{1}{x}\right)}^2=100\\ & \Rightarrow x+\frac{1}{x}=10\\ & \text{Cubing}\text{both}\text{sides}\\ & \Rightarrow x^3+\frac{1}{x^3}=10^3-3\times 10\\ & \Rightarrow x^3+\frac{1}{x^3}=1000-3\times 10\\ & \Rightarrow x^3+\frac{1}{x^3}=970\end{array}$$