Sol. $y=\log _e\left(\frac{1-\mathrm{x}^2}{1+\mathrm{x}^2}\right)$ $$ \frac{d y}{d x}=y^{\prime}=\frac{-4 x}{1-x^4} $$ Again, $$ \frac{d^2 y}{d x^2}=y^{\prime \prime}=\frac{-4\left(1+3 x^4\right)}{\left(1-x^4\right)^2} $$ Again $$ y^{\prime}-y^{\prime \prime}=\frac{-4 x}{1-x^4}+\frac{4\left(1+3 x^4\right)}{\left(1-x^4\right)^2} $$ at $\mathrm{x}=\frac{1}{2}$, $$ y^{\prime}-y^{\prime \prime}=\frac{736}{225} $$ Thus $225\left(y^{\prime}-y^{\prime \prime}\right)=225 \times \frac{736}{225}=736$