Why is this approach wrong? 
If $\alpha$ and $\beta$ are the roots of $x^{2} - 4 x - 3$, then find $$\frac{1}{(\alpha-4)^{2}}+\frac{1}{(\beta-4)^{2}}$$


Solution
This is the approach that gives wrong answer.
\begin{array}{l}
x^{2}-4 x-3=0 \\
(x-4)^{2}=19 \\
So, {(\alpha-4)^{2}} {\&(\beta-4)^{2}}=19 \\
\text { Hence, } \frac{1}{(\alpha-4)^{2}}+\frac{1}{(\beta-4)^{2}}=\frac{2}{19}
\end{array}
This is how it is solved :
\begin{array}{l}
x^{2}-4 x-3=0 \\
\alpha^{2}-4 \alpha-3=0 \\
\alpha(\alpha-4)=3 \\
\alpha-4=\frac{3}{\alpha} \\
\& \beta-4=\frac{3}{\beta}
\end{array}
So , $$
\frac{1}{(\alpha-4)^{2}}+\frac{1}{(\beta-4)^{2}}
$$
\begin{array}{l}
=\frac{\alpha^{2}}{9}+\frac{\beta^{2}}{9} \\
=\frac{1}{9}\left(\alpha^{2}+\beta^{2}\right) \\
=\frac{22}{9}
\end{array}
Please tell me why the first approach is wrong .

You did not factorise $x^2-4x-3$ correctly. Actually, $x^2-4x-3=(x-2)^2-4-3=(x-2)^2-7$. We find that $(x-2)^2=7$, and so $x-2=\pm\sqrt{7}$. Therefore, $x-4=-2\pm\sqrt{7}$, and $(x-4)^2=11\pm4\sqrt{7}$. Hence,
$$
\frac{1}{(\alpha-4)^2}+\frac{1}{(\beta-4)^2}=\frac{1}{11+4\sqrt{7}}+\frac{1}{11-4\sqrt{7}}=\frac{11-4\sqrt{7}+11+4\sqrt{7}}{121-112}=\frac{22}{9} \, .
$$
An alternative method (which would be slower in this case), would be to make the substitution $w=x-4$. The resulting quadratic in $w$ will have roots $\alpha-4$, and $\beta-4$.
