\(The\ planes: 2x-y+4z=5 \ and \ 5x-2.5y+10z=6\ are\)
passes through \((0,0,\frac 54)\)
The equations of the planes are
\(2x - y + 4z = 5\) \(.....(1)\)
\(5x - 2.5y + 10z = 6\) \(.....(2)\)
It can be seen that,
\(\frac {a_1}{a_2} =\frac {2}{5}\)
\(\frac {b_1}{b_2}=\frac {-1}{-2.5}=\frac {2}{5 }\)
\(\frac {c_1}{c_2} =\frac {4}{10} = \frac {2}{5}\)
\(∴\frac {a_1}{a_2}=\frac {b_1}{b_2}=\frac {c_1}{c_2}\)
Therefore, the given planes are parallel.
Hence, the correct answer is B.
Let the lines $L_1 : \vec r = \hat i + 2\hat j + 3\hat k + \lambda(2\hat i + 3\hat j + 4\hat k)$, $\lambda \in \mathbb{R}$ and $L_2 : \vec r = (4\hat i + \hat j) + \mu(5\hat i + + 2\hat j + \hat k)$, $\mu \in \mathbb{R}$ intersect at the point $R$. Let $P$ and $Q$ be the points lying on lines $L_1$ and $L_2$, respectively, such that $|PR|=\sqrt{29}$ and $|PQ|=\sqrt{\frac{47}{3}}$. If the point $P$ lies in the first octant, then $27(QR)^2$ is equal to}

