JEE Main2015MathematicsStraight LinesActual
A straight line L through the point ( 3 , - 2 ) is inclined at an angle of 60 ° to the line 3 x + y = 1 . If L also intersects the X -axis, then the equation of L is:
Options
- Ay + 3 x + 2 - 3 3 = 0
- B3 y - x + 3 + 2 3 = 0
- C3 y + x - 3 + 2 3 = 0
- Dy - 3 x + 2 + 3 3 = 0
Correct answer
D. y - 3 x + 2 + 3 3 = 0
Step-by-step solution
Let m be the slope of the line, then tan ⁡ 60 o = m + 3 1 - m 3 ⇒ 3 = m + 3 1 - 3   m ⇒ ± 3 = m + 3 1 - 3   m ∴ 3 - 3 m = m + 3 or - 3 + 3 m = m + 3 4 m = 0 or 2 m = 2 3 m = 0 or m = 3 Since L intersects X -axis we take m = 3 and get y = 3 x + c Since it passes through 3 , - 2 , therefore line will become   y - 3 x + 2 + 3 3 = 0