Given line
The line is
x + 3 − 3 = y − 1 1 = z − 5 5 . \frac{x+3}{-3}=\frac{y-1}{1}=\frac{z-5}{5}. − 3 x + 3 = 1 y − 1 = 5 z − 5 .
Its point-direction form can be read as:
A point on the line: P ( − 3 , 1 , 5 ) P(-3,1,5) P ( − 3 , 1 , 5 )
Direction vector: d ⃗ 1 = ( − 3 , 1 , 5 ) \vec d_1 = (-3,1,5) d 1 = ( − 3 , 1 , 5 )
So the given line is
r ⃗ = ( − 3 , 1 , 5 ) + λ ( − 3 , 1 , 5 ) . \vec r = (-3,1,5) + \lambda(-3,1,5). r = ( − 3 , 1 , 5 ) + λ ( − 3 , 1 , 5 ) .
Condition for two lines to be coplanar
Two lines are coplanar if the scalar triple product of:
direction vector of first line,
direction vector of second line,
vector joining one point on first line to one point on second line,
is zero.
That is,
[ d ⃗ 1 , d ⃗ 2 , P 1 P 2 → ] = 0. [\vec d_1,\vec d_2,\overrightarrow{P_1P_2}] = 0. [ d 1 , d 2 , P 1 P 2 ] = 0.
Check each option
We take P 1 = ( − 3 , 1 , 5 ) P_1=(-3,1,5) P 1 = ( − 3 , 1 , 5 ) and d ⃗ 1 = ( − 3 , 1 , 5 ) \vec d_1=(-3,1,5) d 1 = ( − 3 , 1 , 5 ) .
Option A
x + 1 − 1 = y − 2 2 = z − 5 4 \frac{x+1}{-1}=\frac{y-2}{2}=\frac{z-5}{4} − 1 x + 1 = 2 y − 2 = 4 z − 5
Point: Q A = ( − 1 , 2 , 5 ) Q_A=(-1,2,5) Q A = ( − 1 , 2 , 5 )
Direction vector:
d ⃗ A = ( − 1 , 2 , 4 ) \vec d_A = (-1,2,4) d A = ( − 1 , 2 , 4 )
Vector joining points:
P 1 Q A → = ( − 1 + 3 , 2 − 1 , 5 − 5 ) = ( 2 , 1 , 0 ) \overrightarrow{P_1Q_A} = (-1+3,2-1,5-5)=(2,1,0) P 1 Q A = ( − 1 + 3 , 2 − 1 , 5 − 5 ) = ( 2 , 1 , 0 )
Now compute scalar triple product:
∣ − 3 1 5 − 1 2 4 2 1 0 ∣ \begin{vmatrix}
-3 & 1 & 5 \\
-1 & 2 & 4 \\
2 & 1 & 0
\end{vmatrix} − 3 − 1 2 1 2 1 5 4 0
Expanding:
= − 3 ∣ 2 4 1 0 ∣ − 1 ∣ − 1 4 2 0 ∣ + 5 ∣ − 1 2 2 1 ∣ = -3\begin{vmatrix}2 & 4 \\ 1 & 0\end{vmatrix}
-1\begin{vmatrix}-1 & 4 \\ 2 & 0\end{vmatrix}
+5\begin{vmatrix}-1 & 2 \\ 2 & 1\end{vmatrix} = − 3 2 1 4 0 − 1 − 1 2 4 0 + 5 − 1 2 2 1
= − 3 ( 2 ⋅ 0 − 4 ⋅ 1 ) − ( − 1 ⋅ 0 − 4 ⋅ 2 ) + 5 ( ( − 1 ) ( 1 ) − 2 ⋅ 2 ) = -3(2\cdot 0 - 4\cdot 1) - ( -1\cdot 0 - 4\cdot 2 ) + 5((-1)(1)-2\cdot 2) = − 3 ( 2 ⋅ 0 − 4 ⋅ 1 ) − ( − 1 ⋅ 0 − 4 ⋅ 2 ) + 5 (( − 1 ) ( 1 ) − 2 ⋅ 2 )
= − 3 ( − 4 ) − ( − 8 ) + 5 ( − 1 − 4 ) = 12 + 8 − 25 = − 5 ≠ 0 = -3(-4) - (-8) + 5(-1-4)
=12+8-25=-5 \neq 0 = − 3 ( − 4 ) − ( − 8 ) + 5 ( − 1 − 4 ) = 12 + 8 − 25 = − 5 = 0
So A is not coplanar .
Option B
x + 1 − 1 = y − 2 2 = z − 5 5 \frac{x+1}{-1}=\frac{y-2}{2}=\frac{z-5}{5} − 1 x + 1 = 2 y − 2 = 5 z − 5
Point: Q B = ( − 1 , 2 , 5 ) Q_B=(-1,2,5) Q B = ( − 1 , 2 , 5 )
Direction vector:
d ⃗ B = ( − 1 , 2 , 5 ) \vec d_B = (-1,2,5) d B = ( − 1 , 2 , 5 )
Vector joining points:
P 1 Q B → = ( 2 , 1 , 0 ) \overrightarrow{P_1Q_B}=(2,1,0) P 1 Q B = ( 2 , 1 , 0 )
Scalar triple product:
∣ − 3 1 5 − 1 2 5 2 1 0 ∣ \begin{vmatrix}
-3 & 1 & 5 \\
-1 & 2 & 5 \\
2 & 1 & 0
\end{vmatrix} − 3 − 1 2 1 2 1 5 5 0
Expanding:
= − 3 ∣ 2 5 1 0 ∣ − 1 ∣ − 1 5 2 0 ∣ + 5 ∣ − 1 2 2 1 ∣ = -3\begin{vmatrix}2 & 5 \\ 1 & 0\end{vmatrix}
-1\begin{vmatrix}-1 & 5 \\ 2 & 0\end{vmatrix}
+5\begin{vmatrix}-1 & 2 \\ 2 & 1\end{vmatrix} = − 3 2 1 5 0 − 1 − 1 2 5 0 + 5 − 1 2 2 1
= − 3 ( 2 ⋅ 0 − 5 ⋅ 1 ) − ( ( − 1 ) ⋅ 0 − 5 ⋅ 2 ) + 5 ( ( − 1 ) ( 1 ) − 2 ⋅ 2 ) = -3(2\cdot 0-5\cdot 1) -((-1)\cdot 0-5\cdot 2)+5((-1)(1)-2\cdot 2) = − 3 ( 2 ⋅ 0 − 5 ⋅ 1 ) − (( − 1 ) ⋅ 0 − 5 ⋅ 2 ) + 5 (( − 1 ) ( 1 ) − 2 ⋅ 2 )
= − 3 ( − 5 ) − ( − 10 ) + 5 ( − 5 ) = 15 + 10 − 25 = 0 = -3(-5)-(-10)+5(-5)=15+10-25=0 = − 3 ( − 5 ) − ( − 10 ) + 5 ( − 5 ) = 15 + 10 − 25 = 0
So B is coplanar .
Option C
x − 1 − 1 = y − 2 2 = z − 5 5 \frac{x-1}{-1}=\frac{y-2}{2}=\frac{z-5}{5} − 1 x − 1 = 2 y − 2 = 5 z − 5
Point: Q C = ( 1 , 2 , 5 ) Q_C=(1,2,5) Q C = ( 1 , 2 , 5 )
Direction vector:
d ⃗ C = ( − 1 , 2 , 5 ) \vec d_C=(-1,2,5) d C = ( − 1 , 2 , 5 )
Vector joining points:
P 1 Q C → = ( 1 + 3 , 2 − 1 , 5 − 5 ) = ( 4 , 1 , 0 ) \overrightarrow{P_1Q_C}=(1+3,2-1,5-5)=(4,1,0) P 1 Q C = ( 1 + 3 , 2 − 1 , 5 − 5 ) = ( 4 , 1 , 0 )
Scalar triple product:
∣ − 3 1 5 − 1 2 5 4 1 0 ∣ \begin{vmatrix}
-3 & 1 & 5 \\
-1 & 2 & 5 \\
4 & 1 & 0
\end{vmatrix} − 3 − 1 4 1 2 1 5 5 0
Expanding:
= − 3 ∣ 2 5 1 0 ∣ − 1 ∣ − 1 5 4 0 ∣ + 5 ∣ − 1 2 4 1 ∣ = -3\begin{vmatrix}2 & 5 \\ 1 & 0\end{vmatrix}
-1\begin{vmatrix}-1 & 5 \\ 4 & 0\end{vmatrix}
+5\begin{vmatrix}-1 & 2 \\ 4 & 1\end{vmatrix} = − 3 2 1 5 0 − 1 − 1 4 5 0 + 5 − 1 4 2 1
= − 3 ( − 5 ) − ( ( − 1 ) ⋅ 0 − 5 ⋅ 4 ) + 5 ( ( − 1 ) ( 1 ) − 2 ⋅ 4 ) = -3(-5)-((-1)\cdot 0-5\cdot 4)+5((-1)(1)-2\cdot 4) = − 3 ( − 5 ) − (( − 1 ) ⋅ 0 − 5 ⋅ 4 ) + 5 (( − 1 ) ( 1 ) − 2 ⋅ 4 )
= 15 − ( − 20 ) + 5 ( − 9 ) = 15 + 20 − 45 = − 10 ≠ 0 =15-(-20)+5(-9)=15+20-45=-10\neq 0 = 15 − ( − 20 ) + 5 ( − 9 ) = 15 + 20 − 45 = − 10 = 0
So C is not coplanar .
Option D
x + 1 1 = y − 2 2 = z − 5 5 \frac{x+1}{1}=\frac{y-2}{2}=\frac{z-5}{5} 1 x + 1 = 2 y − 2 = 5 z − 5
Point: Q D = ( − 1 , 2 , 5 ) Q_D=(-1,2,5) Q D = ( − 1 , 2 , 5 )
Direction vector:
d ⃗ D = ( 1 , 2 , 5 ) \vec d_D=(1,2,5) d D = ( 1 , 2 , 5 )
Vector joining points:
P 1 Q D → = ( 2 , 1 , 0 ) \overrightarrow{P_1Q_D}=(2,1,0) P 1 Q D = ( 2 , 1 , 0 )
Scalar triple product:
∣ − 3 1 5 1 2 5 2 1 0 ∣ \begin{vmatrix}
-3 & 1 & 5 \\
1 & 2 & 5 \\
2 & 1 & 0
\end{vmatrix} − 3 1 2 1 2 1 5 5 0
Expanding:
= − 3 ∣ 2 5 1 0 ∣ − 1 ∣ 1 5 2 0 ∣ + 5 ∣ 1 2 2 1 ∣ = -3\begin{vmatrix}2 & 5 \\ 1 & 0\end{vmatrix}
-1\begin{vmatrix}1 & 5 \\ 2 & 0\end{vmatrix}
+5\begin{vmatrix}1 & 2 \\ 2 & 1\end{vmatrix} = − 3 2 1 5 0 − 1 1 2 5 0 + 5 1 2 2 1
= − 3 ( − 5 ) − ( 1 ⋅ 0 − 5 ⋅ 2 ) + 5 ( 1 ⋅ 1 − 2 ⋅ 2 ) = -3(-5) - (1\cdot 0-5\cdot 2)+5(1\cdot 1-2\cdot 2) = − 3 ( − 5 ) − ( 1 ⋅ 0 − 5 ⋅ 2 ) + 5 ( 1 ⋅ 1 − 2 ⋅ 2 )
= 15 − ( − 10 ) + 5 ( − 3 ) = 15 + 10 − 15 = 10 ≠ 0 =15-(-10)+5(-3)=15+10-15=10\neq 0 = 15 − ( − 10 ) + 5 ( − 3 ) = 15 + 10 − 15 = 10 = 0
So D is not coplanar .
Conclusion
Only Option B satisfies the coplanarity condition.
Therefore, the required line is
x + 1 − 1 = y − 2 2 = z − 5 5 \boxed{\frac{x+1}{-1}=\frac{y-2}{2}=\frac{z-5}{5}} − 1 x + 1 = 2 y − 2 = 5 z − 5