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If x, y, zR+ and 1616 x2+y2-4 xy=z(16 x+4 y-z), then

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Important Questions on Sequences and Series

MEDIUM
Let f:xy be such that f1=2 and fx+y=fxfy for all natural numbers x and y . If k=1 n f( a+k )=16( 2 n 1 ) then a is equal to
MEDIUM
The quotient when 1+x2+x4+...+x34 is divided by 1+x+x2+...+x17 is
MEDIUM
The sum of the first 20 terms of the series 1+32+74+158+3116+ is
HARD
Let fx be a non-constant polynomial with real coefficients such that f12=100 & fx100 for all real x. Which of the following statements is NOT necessarily true?
MEDIUM
The sum of first 20 terms of the sequence 0.7, 0.77, 0.777, ......, is :
MEDIUM
Let C0 be a circle of radius 1. For n1, let Cn be a circle whose area equals the area of a square inscribed in Cn-1. Then u=0areaCi equals,
HARD
Let x,y,z be three non-negative integers such that x+y+z=10. The maximum possible value of xyz+xy+yz+zx is
MEDIUM
If the 2nd, 5th and 9th terms of a non-constant arithmetic progression are in geometric progression, then the common ratio of this geometric progression is
MEDIUM
The sum of the 3rd and the 4th terms of a G.P. is 60 and the product of its first three terms is 1000. If the first term of this G.P. is positive, then its 7th term is:
MEDIUM
Three positive numbers form an increasing G.P. If the middle term in this G.P. is doubled, the new numbers are in A.P. Then the common ratio of the G.P. is :
HARD

If m is the A.M. of two distinct real numbers I and n I, n>1  and G1, G2 and G3 are three geometric means between I and n, then G14+2G24+G34 equals

MEDIUM
Let a, b and c be the 7th, 11th and 13th terms respectively of a non-constant A.P. If these are also the three consecutive terms of a G.P., then ac is equal to:
MEDIUM
If (10)9+2(11)1(10)8+3(11)2(10)7+......+10(11)9 =k(10)9, then k is equal to :
HARD

Let S1 be the sum of areas of the squares whose sides are parallel to coordinate axes. Let S2 be the sum of areas of the slanted squares as shown in the figure. Then S1/S2 is

Question Image

MEDIUM
Let z=1+ai, be a complex number, a>0, such that z3 is a real number. Then, the sum 1+z+z2+.+z11 is equal to :
HARD
Let x, y, z be positive real numbers such that x+y+z=12 and x3y4z5=0.16003. Then x3+y3+z3 is equal to
HARD
For x R, x-1, if 1+x2016+x1+x2015+x21+x2014++x2016= i=0 2016 a i x i , then a17 is equal to
MEDIUM
Suppose p, q, r are real numbers such that q=p4-p, r=q4-q, p=r4-r. The maximum possible value of p+q+r is
HARD
The number of real solutions of the equation sin-1i=1xi+1-xi=1x2i=π2-cos-1i=1 -x2i-i=1-xi lying in the interval -12,12 is____.

(Here, the inverse trigonometric functions sin-1x & cos-1x assume values in -π2,π2 & 0,π

respectively.)
HARD
Let bi>1 for i=1, 2,.,101. Suppose logeb1,logeb2,..,logeb101 are in Arithmetic Progression (A.P.) with the common difference loge2.  Suppose a1, a2,.,a101 are in A.P. such that a1=b1 and a51=b51. If t=b1+b2++b51 and s=a1+a2++a51, then