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Question 1.Let y = y(x) be the solution of the differential equation, xy'-y = x2(xcosx+sinx),x > 0. If y(π) = π, then y’’(π/2)+y(π/2) is equal to:
Solution:
xy’-y = x2(x cosx + sinx) x > 0, y(π) =π
y'-(1/x)y = x(x cosx+sin x)
I.F =
= e- ln x
= 1/x
y(1/x) = ∫(1/x)x(x cos x+sin x) dx
(y/x) = ∫(x cos x+ sin x) dx
(y/x) = ∫ (d/dx)(x sin x) dx
(y/x) = x sin x+C
y = x2 sin x+Cx
x = π, y = π
π = πC
C = 1
y = x2 sin x+x
y(π/2) = (π2/4)+(π/2)
y' = 2x sinx+x2cosx+1
y’’ = 2sinx+2xcosx+2x cosx-x2sinx
y’’(π/2) = 2-(π2/4)
y(π/2)+ y’’(π/2) = 2+π/2
Answer:(b)
Question 2. The value of
Solution:
= 50C6+49C6+48C6+…+31C6+30C6
Add and subtract 30C7
Using nCr+ nCr-1 = n+1Cr
30C6+30C7 = 31C7
31C6+31C7 = 32C7
Similarly solving
51C7-30C7
Answer: (a)
Question 3. Let [t] denote the greatest integer ≤ t. Then the equation in x, [x]2+2[x+2]-7 = 0 has:
Solution:
[x]2+2[x+2]-7 = 0
[x]2 +2[x]-3 = 0
let [x] = y
y2+3y-y -3 = 0
(y -1)(y+3) = 0
[x] = 1 or [x] = -3
x ∈ [1,2) or x ∈ [-3,-2)
Answer: (b)
Question 4. Let P(3, 3) be a point on the hyperbola, (x2/a2)-(y2/b2) = 1. If the normal to it at P intersects the x-axis at (9, 0) and e is its eccentricity, then the ordered pair (a2, e2) is equal to:
Solution:
(x2/a2)-(y2/b2) = 1
Point P(3, 3) on hyperbola.
(9/a2)-(9/b2) = 1 ..(i)
Equation of normal (a2x/3)+(b2y)/3 = a2e2
At x axis y = 0
a2x/3 = a2e2
x = 3e2 = 9
3e2 = 9
e2 = 3
e = √3
e2 = 1+b2/a2 = 3
b2 = 2a2 ..(ii)
Put in equation 1
(9/a2)-(9/2a2) = 1
(9/2a2) = 1
a2 = 9/2
(a2, e2) = (9/2,3)
Answer: (c)
Question 5. Let (x2/a2)+(y2/b2) = 1 (a>b) be a given ellipse, length of whose latus rectum is 10. If its eccentricity is the maximum value of the function, Φ(t) = (5/12)+t-t2, then a2+b2 is equal to:
Solution:
L.R = 2b2/a = 10 ..(i)
Φ(t) = (5/12)-(t-1/2)2+(1/4)
= (8/12)-(t-1/2)2
Φ(t)max = 2/3 = e
e2 = 1-(b2/a2)
= 4/9
b2/a2 = 5/9
From (i)
b2/a.a = 5/9
5/a = 5/9
a = 9
b2 = 45
a2+b2 = 81+45 = 126
Answer: (c)
Question 6. Let
Solution:
Substituting x = tan2t
dx = 2tan t sec2t dt
f(x) =
f(x) = 2∫sin2t dt
x = 3 t = π/3
x = 1 t = π/4
Answer: (d)
Question 7. If 1+(1-22×1)+(1-42×3)+(1-62×5)+......+(1-202×19) = α - 220β, then an ordered pair (α, β) is equal to:
Solution:
Tn = 1-(2n)2(2n-1)
= 1-4n2(2n-1)
= 1-8n3+4n2
Sn =
= n-∑8n3+∑4n2
= n-8×(n2(n+1)2/4)+4n(n+1)(2n+1)/6
S10 = 10-2×100×121 +(2/3)×10×11×21
= 10-24200+1540
= 10-22660
Sum of series = 11-220×103
= α - 220β
α = 11
β = 103
Answer: (b)
Question 8. The integral
Solution:
= tan x-(x sec x/(x sin x+cos x))+C
Answer: (a)
Question 9. Let f(x)= |x-2| and g(x) = f(f(x)) ,x∈0,4]. Then
Solution:
f(x) = |x-2| =
g(x) = ||x-2|-2| =
=
=
= [(1/2)×2×2+1+(1/2)×1×1]-[(1/2)×2×2+(1/2)×1×1)]
= (7/2)-(5/2)
= 1
Answer: (c)
Question 10. Let x0 be the point of local maxima of f(x) =
Solution:
=
= x(x2-2)+2(-2x+7)+ 3(4-7x)
= x3-2x- 4x+14+12-21x
f(x) = x3- 27x+26
f’(x) = 3x2-27 = 0
x = 3
f’’(x) = 6x
at x = 3, f” (3) = 6×3= 18 > 0
at x = -3, f” (-3) = 6×3 = -18 < 0
Max at x0 = -3
So
= 6+6-3-14+6+3-21+4-9
= 25-47
= -22
Answer: (a)
Question 11.A triangle ABC lying in the first quadrant has two vertices as A(1,2) and B(3,1). If BAC = 900 and ar(ΔABC) = 5√5 s units, then the abscissa of the vertex C is:
Solution:
AB = √(4+1) = √5
(1/2)×√5×x = 5√5
x = 10
mAB = -1/2
mAC = 2 = tanθ
Since sinθ = 2/√5
cosθ = 1/√5
by parametric co-ordinates
a = 1+ xcosθ = 1+10×1/√5
= 1+2√5
Answer: (b)
Question 12.Let f be a twice differentiable function on (1,6). If f(2) = 8, f’(2) = 5, f’(x) ≥1 and f’’(x) ≥4, for all x ∈ (1,6), then:
Solution:
f(2) = 8, f’(2) = 5, f’(x) ≥1 and f’’(x) ≥4,
x∈(1,6)
adding (1) and (2) we get,
f(5)+f’(5) ≥28
Answer: (a)
Question 13.Let α and β be the roots of x2-3x+p = 0 and 1/γ and 1/δ be the roots of x2-6x+q = 0. If α, β, γ, δ form a geometric progression. Then ratio (2q+p): (2q-p) is:
Solution:
Roots of x2-3x+p = 0 are α and β.
The roots of x2-6x+q = 0 are γ and δ.
α + β = 3
γ + δ = 6
α = a , β = ar, γ = ar2, δ = ar3
a(1+r) = 3 ...(i)
ar2(1+r) = 6 ...(ii)
Divide (ii) by (i)
r2 = 2
α.β = p = a2r
γ.δ = q = a2r5
(2q+p)/(2q-p) = (2r4+1)/( 2r4-1)
= (2×22+1)/( 2×22-1) = 9/7
Answer: (b)
Question 14. Let u = (2z+i)/(z-ki), z = x+iy and k>0. If the curve represented by Re(u) +Im(u) =1 intersects the y-axis at the points P and Q where PQ =5, then the value of k is:
Solution:
u = (2z+i)/(z-ki)
z = x+iy
Re(u)+Img(u) = 1
2x2+(2y+1)(y -k )+x+2xk = x2 + (y-k)2
at y - axis, x = 0
(2y +1)(y- k) = (y- k )2
2y2 +y- 2yk- k = y2+k2-2yk
Roots of y2+y-(k +k2) = 0 are y1 and y2
Diff. of roots = 5
√(1+4k+4k2) = 5
4k2+4k = 24
k2+k-6 = 0
(k +3)(k-2) = 0
k = 2
Answer: (c)
Question 15. If A =
Solution:
A =
A2 =
a = d = cos (5θ)
b = c = i sin (5θ)
a2-b2 = cos25θ + sin25θ
= 1
Answer: (d)
Question 16. The mean and variance of 8 observations are 10 and 13.5, respectively. If 6 of these observations are 5, 7, 10, 12, 14, 15, then the absolute difference of the remaining two observations is:
Solution:
(5+7+10+12+14+15+x+y)/8 = 10
x+y = 17 ..(i)
Variance = (52+72+102+122+142+152+x2+y2)/8 -100 = 13.5
(739+x2+y2)/8 - 100 = 13.5
x2+y2 = 169 ..(ii)
∴ x = 12, y = 5
|x-y| = 7
Answer: (c)
Question 17. A survey shows that 63% of the people in a city read newspaper A whereas 76% read newspaper B. If x% of the people read both the newspapers, then a possible value of x can be:
Solution:
n(B) ≤n(A∪B) ≤n(U)
76 ≤76+63-x ≤100
-63 ≤-x ≤-39
63 ≥x ≥ 39
Answer (d)
Question 18.Given the following two statements
(S1): (q˅p)→(p ↔ ~q) is a tautology.
(S2): ~q ˄ (~p ↔ q) is a fallacy. Then:
Solution:
Answer (d)
Question 19. Two vertical poles AB = 15 m and CD = 10 m are standing apart on a horizontal ground with points A and C on the ground. If P is the point of intersection of BC and AD, then the height of P (in m) above the line AC is:
Solution:
Using similar triangle concept
tan θ1 = 10/x = H/x1
x1 = Hx/10
tan θ2 = 15/x = H/x2
x2 = Hx/15
Since x1+x2 = x
(Hx/10)+( Hx/15) = x
15H+10H = 150
H = 150/25 = 6 m
Answer: (d)
Question 20. If (a+√2b cos x)( a-√2b cos y) = a2-b2, where a>b>0, then dy/dx at (π/4, π/4) is:
Solution:
(a+√2b cos x)( a-√2b cos y) = a2-b2
Differentiating both sides w.r.t.y
-√2b sin x (dx/dy)(a-√2b cos y)+ (a+√2b cos x)(√2b sin y) = 0
x = y = π/4
-b(dx/dy) (a-b)+(a+b)b = 0
dx/dy = (a+b)/(a-b)
Answer: (a)
Question 21. Suppose a differentiable function f(x) satisfies the identity f(x+y) = f(x)+f(y)+xy2+x2y,for all real x and y. If
Solution:
f(x+y) = f(x)+f(y)+xy2+x2y
x = y = 0
f(0) = 2f(0)
f(0) = 0
Now,
f’(x) = 1+0+x2
f’(x) = 1+x2
f’(3) = 10
Answer: (10)
Question 22.If the equation of a plane P, passing through the intersection of the planes, x+4y-z+7 = 0 and 3x+y+5z = 8 is ax+by+6z = 15 for some a, b∈R, then the distance of the point (3,2,-1) from the plane P is ….. units.
Solution:
p1+λp2 = 0
(x +4y-z+7)+λ(3x+y+5z-8) = ax+by+6z-15
(1+3λ)/a = (4+λ)/b = (-1+5λ)/6 = (7-8λ)/-15
∴ 15-75λ = 42-48λ
-27 = 27λ
= -1
∴ plane is -2x+3y-6z+15 = 0
d = |-6+6+6+15)/√(4+9+36)|
= 3 units
Answer: (3)
Question 23. If the system of equations
x-2y+3z = 9
2x+y+z = b
x-7y+az = 24, has infinitely many solutions, then a-b is equal to:
Solution:
D = 0
1(a +7)+2(2a -1)+3(-14-1) = 0
a+7+4a-2-45 = 0
5a = 40
a = 8
D1 =
9(8+7)+2(8b-24)+3(-7b-24) = 0
135+16b-48-21b-72 = 0
15 = 5b
b = 3
Hence a - b = 8-3 = 5
Answer: (5)
Question 24.Let (2x2+3x+4)10 =
Solution:
Given (2x2+3x+4)10 =
Replace x by 2/x in above identity:
Now, comparing coefficient of x7 from both sides
(take r = 7 in L.H.S. and r = 13 in R.H.S)
210a7 = a13213
a7/a13 = 23 = 8
Answer: (8)
Question 25.The probability of a man hitting a target is 1/10. The least number of shots required, so that the probability of his hitting the target at least once is greater than 1/4 is:
Solution:
Probability of hitting, P(H) = 1/10
probability of missing, P(M) = 9/10
We have, 1-(probability of all shots result in failure ) >1/4
= 1-P(M)n > 1/4
= 1-(9/10)n > 1/4
(9/10)n <3/4
n≥3
Answer (3)