B) 2
Explanation:Expand using binomial:
Numerator:
Denominator:
Limit simplifies:
= 2
So:
✔️ Answer: B
62) If [x] is the greatest integer function and is a real valued function, then f is
A) continuous at x=0
B) continuous at x=1
C) left continuous at x=0
D) right continuous at x=1
View Answer
D) right continuous at x=1
Explanation:At x = 0:
For x → 0⁺:
[x] = 0
⇒ f(x) = (0 − x)/x = −1
For x → 0⁻:
[x] = −1
⇒ f(x) = (−2 − x)/(−x) = (2 + x)/x → −∞
So:
LHL ≠ RHL and both ≠ f(0) = 1
⇒ Not continuous at x = 0
⇒ Not left continuous at x = 0
At x = 1:
For x → 1⁻:
[x] = 0
⇒ f(x) = (0 − x)/|x| = −1
For x → 1⁺:
[x] = 1
⇒ f(x) = (2 − x)/x → 1
Value at x = 1:
f(1) = (2×1 − 1)/1 = 1
So:
Right-hand limit = f(1)
⇒ Right continuous at x = 1
63) If and , then the value of at is
A) 1
B) -1
C) 0
D)
View Answer
B) -1
Explanation:Differentiate parametric:
Use:
Simplify:
Result = -1
✔️ Answer: B
64) Domain of derivative of is
A) [2,3]
B)
C)
D) (2,3)
View Answer
D) (2,3)
Explanation:For derivative:
Arguments must be strictly between -1 and 1
Solve:
2<x<3
✔️ Answer: D
65) If , then
A)
B)
C)
D)
View Answer
C)
Explanation:Simplify:
Use identity:
Expression reduces
Differentiate:
Result:
✔️ Answer: C
66) If , x>1 then at x=e,
A) 0
B) 1
C) 2
D) 3
View Answer
D) 3
Explanation:Let log = ln
y = x^{ln x} + (ln x)^x
Differentiate first term:
x^{ln x} = e^{(ln x)^2}
⇒ d/dx = e^{(ln x)^2} · 2(ln x)(1/x)
At x = e:
ln x = 1 ⇒ value = e · (2/e) = 2
Second term:
(ln x)^x = e^{x ln(ln x)}
Derivative:
= (ln x)^x [ ln(ln x) + 1/ln x ]
At x = e:
ln x = 1 ⇒ ln(ln x) = 0
⇒ value = 1·(0 + 1) = 1
Total:
dy/dx = 2 + 1 = 3
67) If the curves y² = 12x−3 and y² = 12−kx cut each other orthogonally then the length of the sub tangent at (1,b) on the curve y² = 12−kx is
A) 4
B) 6
C) 5
D) 12
View Answer
B) 6
Explanation:Curves:
y² = 12x − 3
y² = 12 − kx
Orthogonal ⇒ product of slopes = −1
Slope1:
2y dy/dx = 12 ⇒ dy/dx = 6/y
Slope2:
2y dy/dx = −k ⇒ dy/dx = −k/(2y)
⇒ (6/y)(−k/(2y)) = −1
⇒ −6k/(2y²) = −1
⇒ 3k = y²
At intersection:
From first:
y² = 12x − 3
Put x = 1:
y² = 9 ⇒ y = ±3
⇒ 3k = 9 ⇒ k = 3
Now for curve y² = 12 − 3x:
Slope:
dy/dx = −3/(2y)
At (1,3):
dy/dx = −1/2
Subtangent length:
= y / (dy/dx) = 3 / (−1/2) = −6
Length = 6
68) A rod of length 41 m with an end A on the floor and another end B on the wall perpendicular to the floor is sliding away horizontally from the wall at the rate of 3 ft/min. When the end B is at the height of 9 ft from the floor, then the rate at which the area of the triangle formed by the rod with wall and floor changes at that instant is (in ft/min)
A)
B)
C)
D)
View Answer
A)
Explanation:Rod length = 41 ft
Let base = x, height = y
x² + y² = 41² = 1681
Given:
dx/dt = 3 ft/min
At y = 9:
x² = 1681 − 81 = 1600 ⇒ x = 40
Differentiate:
2x dx/dt + 2y dy/dt = 0
⇒ 40(3) + 9(dy/dt) = 0
⇒ 120 + 9 dy/dt = 0
⇒ dy/dt = −120/9 = −40/3
Area:
A = (1/2)xy
dA/dt = (1/2)(x dy/dt + y dx/dt)
= (1/2)(40·(−40/3) + 9·3)
= (1/2)(−1600/3 + 27)
= (1/2)(−1519/3)
= −1519/6
Rate of change (magnitude):
1519/6
69) There is a possible error of 0.02 cm in measuring the base diameter of a right circular cone as 14 cm. If the semi-vertical angle of the cone is 45°, then the ap proximate error in its volume is (in cu. cm)
A) 1.078
B) 3.08
C) 1.54
D) 6.16
View Answer
C) 1.54
Explanation:Volume of cone:
Error:
Substitute values:
=1.54
✔️ Answer: C
70) The real valued function is
A) decreasing in (1,∞)
B) increasing in (1,∞)
C) increasing in (-∞,0)
D) decreasing in (0,∞)
View Answer
B) increasing in (1,∞)
Explanation:Differentiate:
f'(x)>0 for x>1
Thus increasing
✔️ Answer: B
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