If the point (λ, λ + 1) lies inside the region bounded by the curve and y - axis, then λ belongs to the interval
Given that the point (λ, λ + 1) lies inside the region bounded by the curve and y - axis.
The curve is rewritten as,
⇒ x2 = 25 - y2
⇒ x2 + y2 = 25
⇒ S = x2 + y2 - 25
We know that for a point (a, b) to lie inside the circle S, the condition to be satisfied is S11<0.
Applying S11<0 for 1st circle,
⇒ λ2 + (λ + 1)2 - 25<0
⇒ λ2 + λ2 + 2λ + 1 - 25<0
⇒ 2λ2 + 2λ - 24<0
⇒ λ2 + λ - 12<0
⇒ λ2 + 4λ - 3λ - 12<0
⇒ λ(λ + 4) - 3(λ + 4)<0
⇒ (λ - 3)(λ + 4)<0
We know that the solution set of (x - a)(x - b)<0 for b>a is (a,b).
The solution set for λ is (- 4,3) ...... (1)
Since the point lies inside y - axis λ + 1>0
⇒ λ> - 1 ..... (2)
The resultant solution set is the intersection of (1) and (2).
⇒ λ((- 4,3)∩(- 1,∞))
⇒ λ(- 1,3)
∴ The correct option is (a).