NCERT Class XI Mathematics - Straight Lines - Solutions

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Question : 34
Total: 74
By using the concept of equation of a line, prove that the three points (3, 0), (– 2, – 2) and (8, 2) are collinear.
Solution:  
Let the given points be A(3, 0), B(–2, –2) and C(8, 2). Then the equation of the line passing through A and B is
y0
x3
=
20
23
y
x3
=
2
5
⇒ 5y = 2x - 6
Clearly the point C(8, 2) satisfy the equation 2x – 5y – 6 = 0.
(Since 2(8) – 5(2) – 6 = 16 – 10 – 6 = 0)
Hence, the given points lie on the same straight line whose equation is 2x – 5y – 6 = 0.
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