BITSAT2010MathematicsStraight LinesActual
The reflection of the point ((4,-13) ) in the line (5 x+y+6=0 ), is
Options
- A((-1,-14) )
- B((3,4) )
- C((1,2) )
- D((-4,13) )
Correct answer
A. ((-1,-14) )
Step-by-step solution
Let ( Q (a, b) ) be the reflection of ( P (4,-13) ) in the line (5 x+y+6=0 ) Then the mid-point (R ( a+4 2 , b-13 2 ) ) lies on ( aligned & 5 x+y+6=0 & 5 ( a+4 2 )+ b-13 2 +6=0 & 5 a+b+19=0 ...(i) aligned ) Also ( PQ ) is perpendicular to (5 x+y+6=0 ) Therefore ( b+13 a-4 (- 5 1 )=-1 ) ( a-5 b-69=0 ...(ii) ) Solving (i) and (ii), we get (a=-1, b=-14 )