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CBSE Class 12 Maths 2010 Solved Paper

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Question : 8 of 29
Marks: +1, -0
Write the vector equation of the following line:
x−53\frac{x-5}{3} = y+47\frac{y+4}{7} = 6−z2\frac{6-z}{2}
Solution:  
The given equation of line is x−53\frac{x-5}{3} = y+47\frac{y+4}{7} = 6−z2\frac{6-z}{2}
i.e in standard form x−53\frac{x-5}{3} = y−(−4)7\frac{y-(-4)}{7} = z−6−2\frac{z-6}{-2}
Comparing this equation with standard form x−x1a\frac{x-x_1}{a} = y−y1b\frac{y-y_1}{b} = z−z1c\frac{z-z_1}{c}
We get, x1x_1 = 5 , y1y_1 = - 4 , z1z_1 = 6 , a = 3 , b = 7 , c = - 2
Thus, the required line is parallel to the vector 3i^+7j^−2k^3\hat{i}+7\hat{j}-2\hat{k} and passes through the point (5, -4, 6).
The vector form of the line can be written as r⃗\vec{r} = a⃗+λb⃗\vec{a}+\lambda\vec{b} , where λ is a constant
Thus, the required equation is r⃗\vec{r} = (5i^−4j^+6k^)(5\hat{i}-4\hat{j}+6\hat{k}) + λ (3i^+7j^−2k^)(3\hat{i}+7\hat{j}-2\hat{k})
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