Advertisements
Advertisements
प्रश्न
The nth term of a sequence is given by an = 2n2 + n + 1. Show that it is not an A.P.
Advertisements
उत्तर
We have:
an = 2n2 + n + 1
\[a_1 = 2 \times 1^2 + 1 + 1 \]
\[ = 4, \]
\[ a_2 = 2 \times 2^2 + 2 + 1\]
\[ = 11\]
\[ a_3 = 2 \times 3^2 + 3 + 1 \]
\[ = 22 \]
\[ a_2 - a_1 = 11 - 4 \]
\[ = 7\]
\[ \text { and } a_3 - a_2 = 22 - 11 \]
\[ = 11\]
\[\text { Since }, a_2 - a_1 \neq a_3 - a_2 \]
\[\text { Hence, it is not an AP } .\]
संबंधित प्रश्न
Find the sum to n terms of the A.P., whose kth term is 5k + 1.
Insert five numbers between 8 and 26 such that the resulting sequence is an A.P.
Find the sum of all numbers between 200 and 400 which are divisible by 7.
Find:
18th term of the A.P.
\[\sqrt{2}, 3\sqrt{2}, 5\sqrt{2},\]
Is 68 a term of the A.P. 7, 10, 13, ...?
The 6th and 17th terms of an A.P. are 19 and 41 respectively, find the 40th term.
How many numbers of two digit are divisible by 3?
The sum of 4th and 8th terms of an A.P. is 24 and the sum of the 6th and 10th terms is 34. Find the first term and the common difference of the A.P.
How many numbers are there between 1 and 1000 which when divided by 7 leave remainder 4?
Find the sum of the following arithmetic progression :
3, 9/2, 6, 15/2, ... to 25 terms
Find the sum of the following serie:
(a − b)2 + (a2 + b2) + (a + b)2 + ... + [(a + b)2 + 6ab]
Find the sum of all integers between 84 and 719, which are multiples of 5.
Find the sum of the series:
3 + 5 + 7 + 6 + 9 + 12 + 9 + 13 + 17 + ... to 3n terms.
The sum of first 7 terms of an A.P. is 10 and that of next 7 terms is 17. Find the progression.
The first term of an A.P. is 2 and the last term is 50. The sum of all these terms is 442. Find the common difference.
The number of terms of an A.P. is even; the sum of odd terms is 24, of the even terms is 30, and the last term exceeds the first by \[10 \frac{1}{2}\] , find the number of terms and the series.
Find the sum of odd integers from 1 to 2001.
In an A.P. the first term is 2 and the sum of the first five terms is one fourth of the next five terms. Show that 20th term is −112.
If \[\frac{1}{a}, \frac{1}{b}, \frac{1}{c}\] are in A.P., prove that:
\[\frac{b + c}{a}, \frac{c + a}{b}, \frac{a + b}{c}\] are in A.P.
Show that x2 + xy + y2, z2 + zx + x2 and y2 + yz + z2 are consecutive terms of an A.P., if x, y and z are in A.P.
If x, y, z are in A.P. and A1 is the A.M. of x and y and A2 is the A.M. of y and z, then prove that the A.M. of A1 and A2 is y.
A farmer buys a used tractor for Rs 12000. He pays Rs 6000 cash and agrees to pay the balance in annual instalments of Rs 500 plus 12% interest on the unpaid amount. How much the tractor cost him?
A carpenter was hired to build 192 window frames. The first day he made five frames and each day thereafter he made two more frames than he made the day before. How many days did it take him to finish the job?
In a cricket team tournament 16 teams participated. A sum of ₹8000 is to be awarded among themselves as prize money. If the last place team is awarded ₹275 in prize money and the award increases by the same amount for successive finishing places, then how much amount will the first place team receive?
If log 2, log (2x − 1) and log (2x + 3) are in A.P., write the value of x.
Sum of all two digit numbers which when divided by 4 yield unity as remainder is
The first and last terms of an A.P. are 1 and 11. If the sum of its terms is 36, then the number of terms will be
If the sum of n terms of an A.P., is 3 n2 + 5 n then which of its terms is 164?
If a1, a2, a3, .... an are in A.P. with common difference d, then the sum of the series sin d [sec a1 sec a2 + sec a2 sec a3 + .... + sec an − 1 sec an], is
Mark the correct alternative in the following question:
If in an A.P., the pth term is q and (p + q)th term is zero, then the qth term is
Mark the correct alternative in the following question:
The 10th common term between the A.P.s 3, 7, 11, 15, ... and 1, 6, 11, 16, ... is
Mark the correct alternative in the following question:
\[\text { If in an A . P } . S_n = n^2 q \text { and } S_m = m^2 q, \text { where } S_r \text{ denotes the sum of r terms of the A . P . , then }S_q \text { equals }\]
If a, b, c are in G.P. and a1/x = b1/y = c1/z, then xyz are in
In an A.P. the pth term is q and the (p + q)th term is 0. Then the qth term is ______.
The first term of an A.P.is a, and the sum of the first p terms is zero, show that the sum of its next q terms is `(-a(p + q)q)/(p - 1)`
Let Sn denote the sum of the first n terms of an A.P. If S2n = 3Sn then S3n: Sn is equal to ______.
