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In a geometric sequence of real numbers, the sum of the first two terms is 7 and the sum of the first six terms is 91. The sum of the first four terms is.

$$\mathrm{In}\:\mathrm{a}\:\mathrm{geometric}\:\mathrm{sequence}\:\mathrm{of}\:\mathrm{real} \\ $$$$\mathrm{numbers},\:\mathrm{the}\:\mathrm{sum}\:\mathrm{of}\:\mathrm{the}\:\mathrm{first} \\ $$$$\mathrm{two}\:\mathrm{terms}\:\mathrm{is}\:\mathrm{7}\:\mathrm{and}\:\mathrm{the}\:\mathrm{sum}\:\mathrm{of}\:\mathrm{the}\:\mathrm{first} \\ $$$$\mathrm{six}\:\mathrm{terms}\:\mathrm{is}\:\mathrm{91}.\:\mathrm{The}\:\mathrm{sum}\:\mathrm{of}\:\mathrm{the}\:\mathrm{first} \\ $$$$\mathrm{four}\:\mathrm{terms}\:\mathrm{is}. \\ $$$$ \\ $$

Question Number 111541 Answers: 3 Comments: 0

How many natural numbers less than 1000 have the sum of their digits equal to 5?

$$\mathrm{How}\:\mathrm{many}\:\mathrm{natural}\:\mathrm{numbers}\:\mathrm{less}\:\mathrm{than} \\ $$$$\mathrm{1000}\:\mathrm{have}\:\mathrm{the}\:\mathrm{sum}\:\mathrm{of}\:\mathrm{their}\:\mathrm{digits}\:\mathrm{equal} \\ $$$$\mathrm{to}\:\mathrm{5}? \\ $$

Question Number 111539 Answers: 1 Comments: 0

In a trapezoid ABCD, sides AB and CD are parallel and side BC=CD=(√5). If DC^ B =120° and BA^ D=60°. Find the area of ABCD.

$$\mathrm{In}\:\mathrm{a}\:\mathrm{trapezoid}\:\mathrm{ABCD},\:\mathrm{sides}\:\mathrm{AB}\:\mathrm{and} \\ $$$$\mathrm{CD}\:\mathrm{are}\:\mathrm{parallel}\:\mathrm{and}\:\mathrm{side}\:\mathrm{BC}=\mathrm{CD}=\sqrt{\mathrm{5}}. \\ $$$$\mathrm{If}\:\mathrm{D}\hat {\mathrm{C}B}\:=\mathrm{120}°\:\mathrm{and}\:\mathrm{B}\hat {\mathrm{A}D}=\mathrm{60}°.\:\mathrm{Find} \\ $$$$\mathrm{the}\:\mathrm{area}\:\mathrm{of}\:\mathrm{ABCD}. \\ $$

Question Number 111537 Answers: 2 Comments: 0

What is the minimum value obtained when an arbitrary number of three different non−zero digits is divided by the sum of its digits?

$$\mathrm{What}\:\mathrm{is}\:\mathrm{the}\:\mathrm{minimum}\:\mathrm{value}\:\mathrm{obtained} \\ $$$$\mathrm{when}\:\mathrm{an}\:\mathrm{arbitrary}\:\mathrm{number}\:\mathrm{of}\:\mathrm{three} \\ $$$$\mathrm{different}\:\mathrm{non}−\mathrm{zero}\:\mathrm{digits}\:\mathrm{is}\:\mathrm{divided} \\ $$$$\mathrm{by}\:\mathrm{the}\:\mathrm{sum}\:\mathrm{of}\:\mathrm{its}\:\mathrm{digits}? \\ $$$$ \\ $$

Question Number 111536 Answers: 2 Comments: 2

Let 2,3,5,6,7,10,11,... be increasing sequence of positive integers that are neither the square nor cube of an integer. Find the 2016th term of this sequence.

$$\mathrm{Let}\:\mathrm{2},\mathrm{3},\mathrm{5},\mathrm{6},\mathrm{7},\mathrm{10},\mathrm{11},...\:\mathrm{be}\:\mathrm{increasing} \\ $$$$\mathrm{sequence}\:\mathrm{of}\:\mathrm{positive}\:\mathrm{integers}\:\mathrm{that}\:\mathrm{are} \\ $$$$\mathrm{neither}\:\mathrm{the}\:\mathrm{square}\:\mathrm{nor}\:\mathrm{cube}\:\mathrm{of}\:\mathrm{an} \\ $$$$\mathrm{integer}.\:\mathrm{Find}\:\mathrm{the}\:\mathrm{2016th}\:\mathrm{term}\:\mathrm{of}\:\mathrm{this} \\ $$$$\mathrm{sequence}. \\ $$

Question Number 111535 Answers: 1 Comments: 0

If f(x)=ax^2 −c satisfy −4≤f(1)≤−1 and −1≤f(2)≤5, then A. 7≤f(3)≤26 B. −1≤f(3)≤20 C. −4≤f(3)≤15 D. ((−28)/3)≤f(3)≤((35)/3) E. (8/3)≤f(3)≤((13)/3)

$$\mathrm{If}\:\mathrm{f}\left(\mathrm{x}\right)=\mathrm{ax}^{\mathrm{2}} −\mathrm{c}\:\mathrm{satisfy}\:−\mathrm{4}\leqslant\mathrm{f}\left(\mathrm{1}\right)\leqslant−\mathrm{1} \\ $$$$\mathrm{and}\:−\mathrm{1}\leqslant\mathrm{f}\left(\mathrm{2}\right)\leqslant\mathrm{5},\:\mathrm{then} \\ $$$$ \\ $$$$\mathrm{A}.\:\mathrm{7}\leqslant\mathrm{f}\left(\mathrm{3}\right)\leqslant\mathrm{26}\:\mathrm{B}.\:−\mathrm{1}\leqslant\mathrm{f}\left(\mathrm{3}\right)\leqslant\mathrm{20}\:\mathrm{C}. \\ $$$$−\mathrm{4}\leqslant\mathrm{f}\left(\mathrm{3}\right)\leqslant\mathrm{15}\:\mathrm{D}.\:\frac{−\mathrm{28}}{\mathrm{3}}\leqslant\mathrm{f}\left(\mathrm{3}\right)\leqslant\frac{\mathrm{35}}{\mathrm{3}}\:\mathrm{E}. \\ $$$$\frac{\mathrm{8}}{\mathrm{3}}\leqslant\mathrm{f}\left(\mathrm{3}\right)\leqslant\frac{\mathrm{13}}{\mathrm{3}} \\ $$

Question Number 111534 Answers: 2 Comments: 0

If x=((1+(√(2016)))/2), then 4x^3 −2019x−2017 equals?

$$\mathrm{If}\:\mathrm{x}=\frac{\mathrm{1}+\sqrt{\mathrm{2016}}}{\mathrm{2}},\:\mathrm{then} \\ $$$$\mathrm{4x}^{\mathrm{3}} −\mathrm{2019x}−\mathrm{2017}\:\mathrm{equals}? \\ $$

Question Number 111533 Answers: 1 Comments: 2

The mean,median and mode of the data values 90,54,x,123,62,78,58,81 are all equal. What is the value of x?

$$\mathrm{The}\:\mathrm{mean},\mathrm{median}\:\mathrm{and}\:\mathrm{mode}\:\mathrm{of}\:\mathrm{the} \\ $$$$\mathrm{data}\:\mathrm{values}\:\mathrm{90},\mathrm{54},\mathrm{x},\mathrm{123},\mathrm{62},\mathrm{78},\mathrm{58},\mathrm{81} \\ $$$$\mathrm{are}\:\mathrm{all}\:\mathrm{equal}.\:\mathrm{What}\:\mathrm{is}\:\mathrm{the}\:\mathrm{value}\:\mathrm{of}\:\mathrm{x}? \\ $$

Question Number 111528 Answers: 3 Comments: 0

(√(bemath)) lim_(x→π/2) (1−sin x)^(cos x) ?