d=λ(b+c)a⋅d=λ(b⋅a+c⋅a)1=λ(1+x+5) 1=λ(x+6) ...(1) $\begin{aligned}
& |\overrightarrow{\mathrm{d}}|=1 \
& |\lambda(\overrightarrow{\mathrm{b}}+\overrightarrow{\mathrm{c}})|=1 \
& |\lambda((\mathrm{x}+2) \hat{\mathrm{i}}+6 \hat{\mathrm{j}}-2 \hat{\mathrm{k}})|=1 \
& \lambda^2\left((\mathrm{x}+2)^2+6^2+2^2\right)=1 \
& \mathrm{x}^2+4 \mathrm{x}+4+36+4=(\mathrm{x}+6)^2 \
& \mathrm{x}^2+4 \mathrm{x}+44=\mathrm{x}^2+12 \mathrm{x}+36 \
& 8 \mathrm{x}=8, \mathrm{x}=1 \
& \left|\begin{array}{ccc}
1 & 1 & 1 \
2 & 4 & -5 \
\mathrm{x} & 2 & 3
\end{array}\right|=(\overrightarrow{\mathrm{a}} \times \overrightarrow{\mathrm{b}}) \cdot \overrightarrow{\mathrm{c}} \
& \left|\begin{array}{ccc}
0 & 0 & 1 \
-2 & 9 & -4 \
\mathrm{x}-2 & -1 & 3
\end{array}\right|=2-9(\mathrm{x}-2) \
& =20-9 \mathrm{x} \
& \text { at } \mathrm{x}=1 \
& 20-9=11
\end{aligned}$