CBSE Class 12 Maths 2010 Solved Paper

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Question : 8
Total: 29
Write the vector equation of the following line:
x−5
3
=
y+4
7
=
6−z
2
Solution:  
The given equation of line is
x−5
3
=
y+4
7
=
6−z
2

i.e in standard form
x−5
3
=
y−(−4)
7
=
z−6
−2

Comparing this equation with standard form
x−x1
a
=
y−y1
b
=
z−z1
c

We get, x1 = 5 , y1 = - 4 , z1 = 6 , a = 3 , b = 7 , c = - 2
Thus, the required line is parallel to the vector 3
^
i
+7
^
j
−2
^
k
and passes through the point (5, -4, 6).
The vector form of the line can be written as
→
r
=
→
a
+λ
→
b
, where λ is a constant
Thus, the required equation is
→
r
= (5
^
i
−4
^
j
+6
^
k
)
+ λ (3
^
i
+7
^
j
−2
^
k
)
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