JEE 2023 Mathematics PYQ — If is the area in the first quadrant enclosed by the curve the ta… | Mathem Solvex | Mathem Solvex
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JEE 2023 — Mathematics PYQ
JEE | Mathematics | 2023
If A is the area in the first quadrant enclosed by the curve C:2x2−y+1=0the tangent to C at the point (1,3) and the line x+y=1then the value of 60A is ______.
Choose the correct answer:
A.
16
(Correct Answer)
B.
15
C.
14
D.
13
Correct Answer:
16
Explanation
Given that y=2x2+1 which is a parabola.
Differentiating: dxdy=4x
dxdy(1,3)=4
⇒ Eqn. of tangent at (1,3) is y−3=4(x−1)
⇒y=4x−1 ...(i)
Solving line (i) with x+y=1 ...(ii)
we get x=52 and y=53
which can be represented as
So, the required area is A=∫01yParaboladx−∫02/5yLine (ii)dx−∫2/51yLine (i)dx
=∫01(2x2+1)dx−∫02/5(1−x)dx−∫2/51(4x−1)dx
=[32x3+x]01−[x−2x2]02/5−[24x2−x]2/51
and 15A=4 or 60A=16
Explanation
Given that y=2x2+1 which is a parabola.
Differentiating: dxdy=4x
dxdy(1,3)=4
⇒ Eqn. of tangent at (1,3) is y−3=4(x−1)
⇒y=4x−1 ...(i)
Solving line (i) with x+y=1 ...(ii)
we get x=52 and y=53
which can be represented as
So, the required area is A=∫01yParaboladx−∫02/5yLine (ii)dx−∫2/51yLine (i)dx