NIMCET 2015 — Mathematics PYQ
NIMCET | Mathematics | 2015If 3x+4y+k=0 is tangent to the hyperbola 9x2−16y2=144, then value of k is:
Choose the correct answer:
- A.
0
(Correct Answer) - B.
1
- C.
-1
- D.
-3
0
Explanation
Standard form of the hyperbola:
1449x2−14416y2=1
16x2−9y2=1
Here, a2=16 and b2=9.
Equation of the line:
4y=−3x−k
y=(−43)x+(−4k)
This is in the form y=mx+c, where m=−43 and c=−4k.
Condition for tangency to a hyperbola a2x2−b2y2=1:
c2=a2m2−b2
Substituting the values:
(−4k)2=16(−43)2−9
16k2=16(169)−9
16k2=9−9
16k2=0
k2=0
k=0
Correct Option: (a)
Explanation
Standard form of the hyperbola:
1449x2−14416y2=1
16x2−9y2=1
Here, a2=16 and b2=9.
Equation of the line:
4y=−3x−k
y=(−43)x+(−4k)
This is in the form y=mx+c, where m=−43 and c=−4k.
Condition for tangency to a hyperbola a2x2−b2y2=1:
c2=a2m2−b2
Substituting the values:
(−4k)2=16(−43)2−9
16k2=16(169)−9
16k2=9−9
16k2=0
k2=0
k=0
Correct Option: (a)