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NCERT Class XI Mathematics - Straight Lines - Solutions

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Question : 77 of 74
Marks: +1, -0
A person standing at the junction (crossing) of two straight paths represented by the equations 2x – 3y + 4 = 0 and 3x + 4y – 5 = 0 wants to reach the path whose equation is 6x – 7y + 8 = 0 in the least time. Find equation of the path that he should follow.
Solution:  
The given equation of lines are
2x – 3y + 4 = 0 ...(i)
and 3x + 4y – 5 = 0 ... (ii)
On solving (i) and (ii), we get x = 117-\frac{1}{17} , y = 2217\frac{22}{17}
∴ Required point is (117,2217)\left(-\frac{1}{17},\frac{22}{17}\right)
Now slope of 6x – 7y + 8 = 0 is 67\frac{6}{7}
∴ Required slope is 76-\frac{7}{6}
Therefore required equation of a line is (y2217)\left(y-\frac{22}{17}\right) = 76(x+117)-\frac{7}{6}\left(x+\frac{1}{17}\right)
⇒ (17y – 22) 6 = – 7(17x + 1)
⇒ 102y – 132 = – 119x – 7
⇒ 119x + 102y – 125 = 0
⇒ 119x + 102y = 125.
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