Math Problems & Solutions: Roots, Polynomials, Locus, Sequences, Geometry, Inequalities, Exercises of Statistics

A collection of mathematical problems covering various topics such as constructing polynomials with given roots, finding double roots of equations, locus of a point, limits of sequences, inscribing pentagons in circles, and proving equations. It also includes problems on alternating sequences.

Typology: Exercises

2019/2020

Uploaded on 08/27/2021

ojas-mehrotra
ojas-mehrotra 🇮🇳

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1. Let ibe a root of the equation x2+ 1 = 0 and let ωbe a root of the
equation x2+x+ 1 = 0. Construct a polynomial
f(x) = a0+a1x+. . . +anxn
where a0, a1, . . . , anare all integers such that f(i+ω)=0.
2. Let abe a fixed real number. Consider the equation
(x+ 2)2(x+ 7)2+a= 0, x R,
where Ris the set of real numbers. For what values of a, will the equation
have exactly one double-root?
3. Let Aand Bbe variable points on x-axis and y-axis respectively such
that the line segment AB is in the first quadrant and of a fixed length
2d. Let Cbe the mid-point of AB and Pbe a point such that
(a) Pand the origin are on the opposite sides of AB and,
(b) P C is a line segment of length dwhich is perpendicular to AB.
Find the locus of P.
4. Let a real-valued sequence {xn}n1be such that
lim
n→∞ nxn= 0.
Find all possible real values of tsuch that limn→∞ xn(log n)t= 0.
5. Prove that the largest pentagon (in terms of area) that can be inscribed
in a circle of radius 1 is regular (i.e., has equal sides).
6. Prove that the family of curves
x2
a2+λ+y2
b2+λ= 1
satisfies dy
dx(a2b2) = (x+ydy
dx) (xdy
dx y).
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  1. Let i be a root of the equation x^2 + 1 = 0 and let ω be a root of the equation x^2 + x + 1 = 0. Construct a polynomial f (x) = a 0 + a 1 x +... + anxn where a 0 , a 1 ,... , an are all integers such that f (i + ω) = 0.
  2. Let a be a fixed real number. Consider the equation (x + 2)^2 (x + 7)^2 + a = 0, x ∈ R, where R is the set of real numbers. For what values of a, will the equation have exactly one double-root?
  3. Let A and B be variable points on x-axis and y-axis respectively such that the line segment AB is in the first quadrant and of a fixed length 2 d. Let C be the mid-point of AB and P be a point such that (a) P and the origin are on the opposite sides of AB and, (b) P C is a line segment of length d which is perpendicular to AB. Find the locus of P.
  4. Let a real-valued sequence {xn}n≥ 1 be such that

nlim→∞ nxn^ = 0. Find all possible real values of t such that limn→∞ xn(log n)t^ = 0.

  1. Prove that the largest pentagon (in terms of area) that can be inscribed in a circle of radius 1 is regular (i.e., has equal sides).
  2. Prove that the family of curves x^2 a^2 + λ +^

y^2 b^2 + λ =^1 satisfies (^) dy dx (a

(^2) − b (^2) ) = (x + y dy dx ) (x

dy dx −^ y).

  1. Consider a right-angled triangle with integer-valued sides a < b < c where a, b, c are pairwise co-prime. Let d = c − b. Suppose d divides a. Then (a) Prove that d ≤ 2. (b) Find all such triangles (i.e. all possible triplets a, b, c) with perime- ter less than 100.
  2. A finite sequence of numbers (a 1 ,... , an) is said to be alternating if a 1 > a 2 , a 2 < a 3 , a 3 > a 4 , a 4 < a 5 ,.... or a 1 < a 2 , a 2 > a 3 , a 3 < a 4 , a 4 > a 5 ,.... How many alternating sequences of length 5, with distinct numbers a 1 ,... , a 5 can be formed such that ai ∈ { 1 , 2 ,... , 20 } for i = 1,... , 5?