NIMCET 2012 — Mathematics PYQ
NIMCET | Mathematics | 2012Focus of the parabola x2+y2−2xy−4(x+y−1)=0 is:
Choose the correct answer:
- A.
(1,1)
(Correct Answer) - B.
(1,2)
- C.
(2,1)
- D.
(0,2)
(1,1)
Explanation
Solution
1. Rearranging the Equation:
2. Identifying Axis and Tangent at Vertex:
-
Axis: x−y=0⟹y=x
-
Tangent at Vertex: x+y−1=0
3. Finding Vertex (V):
Intersection of y=x and x+y−1=0:
4. Finding Focal Length (a):
Length of Latus Rectum (4a) for (x−y)2=4(x+y−1):
5. Calculating Focus (S):
Focus lies on the axis y=x at distance a from Vertex:
Conclusion:
Focus is (1,1).
Correct Option:
(a) (1,1)
Explanation
Solution
1. Rearranging the Equation:
2. Identifying Axis and Tangent at Vertex:
-
Axis: x−y=0⟹y=x
-
Tangent at Vertex: x+y−1=0
3. Finding Vertex (V):
Intersection of y=x and x+y−1=0:
4. Finding Focal Length (a):
Length of Latus Rectum (4a) for (x−y)2=4(x+y−1):
5. Calculating Focus (S):
Focus lies on the axis y=x at distance a from Vertex:
Conclusion:
Focus is (1,1).
Correct Option:
(a) (1,1)

