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Entrance Paper, Study notes of Mathematics

<div><br /></div><div>Closed under addition, closed under multiplication, group homomorphism, positive real numbers, continuous function, number of generators, local maximum, local minimum, uniformly continuous, distance between the straight lines</div><div><br /></div><div><br /></div>

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2010/2011

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Department of Mathematics and Statistics
University of Hyderabad
Note: Throughout this question paper, Nstands for the set of all natural
numbers, Zstands for the set of all integers, Qstands for the set of all rational
numbers , Rstands for the set of all real numbers and Cstands for the set of
all complex numbers.
Part A - 1 mark for each question
1. Let λ=e30πi
36 . Then the smallest positive integer lsuch that λl= 1 is
(a) 6
(b) 9
(c) 12
(d) 5
2. Consider the vector (1,1,1) in R3. Two linearly independent vectors or-
thogonal to it are
(a) (1,-1,1) and (1,1,-2)
(b) (-2,1,1) and (1,1-2)
(c) (1,-1,0) and (2,-2,0)
(d) (0,1,-1) and (0,-2,2)
3. The graph of the polynomial (X22)(X2+X+ 1) will cross the X-axis
(a) 0 times
(b) once
(c) twice
(d) 3 times
4. ”There exists an integer which is not divisible by the square of a prime
number”. The negation of this statement is
(a) There exists an integer which is divisible by the square of a prime
(b) Every integer is not divisible by the square of a prime number
(c) Every integer is divisible by the square of a prime number
(d) There exists many integers divisible by the square of a prime number
5. Let f , g :RRbe continuous functions whose graphs do not intersect.
Then for which function below the graph lies entirely on one side of the
X-axis
(a) f
(b) g+f
1
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Department of Mathematics and Statistics

University of Hyderabad

Note: Throughout this question paper, N stands for the set of all natural numbers, Z stands for the set of all integers, Q stands for the set of all rational numbers , R stands for the set of all real numbers and C stands for the set of all complex numbers.

Part A - 1 mark for each question

  1. Let λ = e 3036 πi^. Then the smallest positive integer l such that λl^ = 1 is (a) 6 (b) 9 (c) 12 (d) 5
  2. Consider the vector (1, 1 , 1) in R^3. Two linearly independent vectors or- thogonal to it are (a) (1,-1,1) and (1,1,-2) (b) (-2,1,1) and (1,1-2) (c) (1,-1,0) and (2,-2,0) (d) (0,1,-1) and (0,-2,2)
  3. The graph of the polynomial (X^2 − 2)(X^2 + X + 1) will cross the X-axis (a) 0 times (b) once (c) twice (d) 3 times
  4. ”There exists an integer which is not divisible by the square of a prime number”. The negation of this statement is (a) There exists an integer which is divisible by the square of a prime (b) Every integer is not divisible by the square of a prime number (c) Every integer is divisible by the square of a prime number (d) There exists many integers divisible by the square of a prime number
  5. Let f, g : R → R be continuous functions whose graphs do not intersect. Then for which function below the graph lies entirely on one side of the X-axis (a) f (b) g + f

(c) g − f (d) gf

  1. An example of a function from R → R^2 with bounded range is (a) f (t) = (t, t^2 ) (b) f (t) = (t, sin t) (c) f (t) = (t, sinh t) (d) f (t) = (sin t, cos t)
  2. The real root of X^3 + X + 1 = 0 lies between (a) -2 and - (b) -1 and 0 (c) 1 and 2 (d) 2 and 3
  3. Which of the following maps is a linear transformation from R^3 to R? (a) T (a, b, c) = a(b + c) (b) T (a, b, c) = 2(a + b + c) (c) T (a, b, c) = ab + c (d) T (a, b, c) = abc
  4. The events A 1 and A 2 occur with probabilities 0.6 and 0.8 respectively. At least one of them occurs with a probablity of 0.9. The probability that both A 1 and A 2 will occur is (a) 0 (b) 0. (c) 1 (d) cannot be determined from the data given
  5. Two students each are randomly placed in n rooms in a hostel. If n of the 2n students are Mathematics students and n are in Statistics, the prob- ablity that each room has Mathematics student and a statistics student is (a) (^21) n! (b) (^21) n! (c) (^2) n^2 Cnn (d) (^) (n^2 n!) 2
  6. How many positive integers a less than 24 satisfy a^8 ≡ 1(mod24)?

(d) 15

  1. f (x) = ex^ − e−x, g(x) = ex^ + e−x^ Then

(a) Both f and g are even functions (b) Both f and g are odd functions (c) f is odd , g is even (d) f is even, g is odd

  1. xn+1 = − 43 xn, x 0 = 1. The sequence {xn}

(a) diverges (b) xn is monotonically increasing and converges to 0 (c) xn is monotonically decreasing and converges to 0 (d) None of the above

  1. f (x) is an odd function, g(x) an even function then

(a) f ◦ g is odd (b) f ◦ g is even (c) f ◦ f is odd (d) g ◦ g is odd

  1. Let X be a set and f, g : X → X be functions. We can say that f ◦ g is bijective if (a) at least one of f , g is bijective (b) both f and g are bijective (c) f is 1 − 1 and g is onto (d) f is onto and g is 1 − 1
  2. Let f : [− 1 , 1] → R be a continuous function such that

− 1 f^ (x)dx^ = 0. Then (a) f ≡ 0 (b) f is an odd function (c)

− 1 / 2

f (x)dx = 0 (d) None of these

  1. Let f, g : R → R be functions. We can conclude that h(x) ≤ f (x) ∀x ∈ R if we define h : R → R as (a) min{g(x), f (x) + g(x)} (b) min{f (x), f (x) + g(x)}

(c) max{g(x), f (x) + g(x)} (d) max{f (x), f (x) + g(x)}

  1. Let X be a non-empty set, f : X → X be a function and let A, B ⊂ X. Then the identity f (A ∩ B) = f (A) ∩ f (B) is true (a) always (b) if f is 1- (c) if f is onto (d) if A ∪ B = X
  2. If n ≥ 1000 is a natural number, the remainder when n^2 + n + 1 is divided by 4 is (a) always 1 (b) always 3 (c) 1 or 3 (d) 0 or 2
  3. Let X be a finite set with 5 elements. Then the number of 1-1 functions from X × X to X × X is (a) 5! (b) (5!)^2 (c) 25! (d) 25!5! Part B - 2 marks for each question
  4. The number of 2 × 2 matrices with integer entries that satisfy the polyno- mial X^2 + X + 1 is (a) atmost 2 (b) exactly 2 (c) infinite (d) none
  5. Let (Q, +) be the group of all rationals under addition and (Q∗ +, .) be the group of positive nonzero rationals under multiplication. Suppose f : Q → Q∗ + is a homomorphism. Then f (17) = (a) 17^2 (b) 17 (c) 171

(a) 648 (b) 504 (c) 120 (d) 324

  1. Let T 1 , T 2 be two linear transformations from a finite dimensional vector space V to another space W. Suppose that T 1 , T 2 are onto. Then (a) dim Ker T 1 =dim Ker T 2 (b) Ker T 1 = Ker T 2 (c) Ker T 1 strictly contained Ker T 2 (d) T 1 = T 2
  2. The orthogonal trajectories of the family of curves x + 2y^2 = c where c is a constant is (a) y = 4x (b) y = − 4 x (c) y = e^4 x (d) y = e−^4 x
  3. A non zero vector common to the space spanned by (1,2,3), (3,2,1) and the space spanned by (1,0,1) and (3,4,3) is (a) (1,2,3) (b) (0,-2,-2) (c) (3,2,0) (d) (1,1,1)
  4. A subset A of C is said to be balanced if whenever a ∈ A and t ∈ R, it is true that aeit^ ∈ A. Which one of these four subsets is balanced? (a) The elliptic region {x + iy | x 42 + y 92 ≤ 1 } (b) The upper half plane {x + iy |y > 0 } (c) The Y -axis {x + iy |y = 0} (d) The annular region {x + iy | 1 ≤ x^2 + y^2 ≤ 2 }
  5. Let A 6 be the set of all positive integers for which 6 is not a factor. Then

(a) A 6 is closed under addition (b) A 6 is closed under multiplication (c) A 6 ∪ 6 N = N (d) A 6 ∪ 6 A 6 = N

  1. Which is not a group homomorphism?

(a) f : (R, +) → (R − { 0 }, .) given by f (x) = xex (b) f : (Q − { 0 }, .) → (Q − { 0 }, .) given by f (x) = 2x (c) f : (N, +) → (R, +) given by f (x) = x + |x| (d) f : (C, +) → (C, +) given by f (x) = 2x

  1. For a real number x, let bxc denote the greatest integer less than or equal to x. Then (a) bxyc ≥ bxcbyc for all x, y ∈ R (b) bxyc ≤ bxcbyc for all x, y ∈ R (c) bxyc ≥ bxc + byc for all x, y ∈ R (d) bxyc ≤ bxc + byc for all x, y ∈ R
  2. Let (xn) be a sequence of positive real numbers. A sufficient condition for (xn) to have no convergent subsequence is (a) |xn+2 − xn+1| > |xn+1 − xn| ∀n ∈ N (b) ∀ i, j ∈ N, the set {n ∈ N : |xi − xn| < (^1) j } is finite (c)

k=1 xnk^ =^ ∞^ for every increasing sequence (nk) of natural num- bers. (d) none of the above

  1. Let P be a real polynomial such that for x ∈ R, P (x) = 0 iff x = 2 or 4. Then (a) degree of P is 2 (b) P (3) < 0 (c) P ′(x) = 0 for some x < 4 (d) P (x) is of the form c(x − 2)n(x − 4)m^ where c is a constant
  2. Let f : R → R be a continuous function with f (0) = 0 and let (xn) be a sequence in R with (^) nlim→∞f (xn) = 0. Then (a) (^) nlim→∞xn = 0 (b) (^) klim→∞xnk = 0, for some subsequence (xnk ) (c) (xn) is bounded (d) none of the above
  3. Number of generators of the group (Z 36 , +) is

(a) 1 (b) 6

(a) − √ˆi 6 +

√2ˆj √ 3 + √kˆ 6

(b) √ˆi 6 −

√2ˆj √ 3 + √ˆk 6 (c) − √ˆi 6 +

√2ˆj √ 3 − √kˆ 6

(d) √ˆi 6 +

√2ˆj √ 3 − √ˆk 6