Click to Chat

1800 2000 838

CART 0

• 0

MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: R

There are no items in this cart.
Continue Shopping
Get instant 20% OFF on Online Material.
coupon code: MOB20 | View Course list

Get extra R 440 off
USE CODE: CART20

				   If the sum of first n terms of an A.P. is cn2, then sum of squares of these n terms is?
ans:n(4n2-1)c2/3

HOW?


4 years ago

Share

										If a is 1st term and d is common difference, sum of n terms = (n/2) (2a + (n-1)d) = (2an-nd) + n2d

comparing this with cn2 we get : 2an-nd = 0  and  d = c    =>    a = c/2,  d = c

sum of squares of n terms = $\sum_{r=1}^{n}(a+(n-1)d)^{2}$

$=\sum_{r=1}^{n}\left( \frac{c}{2}+(n-1)c\right)^{2}$

$=\sum_{r=1}^{n}c^{2}\left( n^{2}-n+\frac{1}{4}\right)$

$=c^{2}\left( \sum_{r=1}^{n}n^{2}-\sum_{r=1}^{n}n+\sum_{r=1}^{n}\frac{1}{4}\right)$

$=c^{2}\left(\frac{n(n+1)(2n+1)}{6}-\frac{n(n+1)}{2}+\frac{n}{4}\right)$

$=\frac{c^{2}n(4n^{2}-1)}{12}$

4 years ago

x+y+z=10,x=1,y=5,z=?

4

 OUTPASS 8 months ago

4

 HARSHAVARDHAN 8 months ago

4

 SAI 8 months ago
why 2+3=5??

 Prabhakar ch one month ago

HI STUDENT ACCORDING TO MATHEMATICS THE ‘+’INDICATES THAT TO ADD.THIS MY REASON ANOTHER REASON I DONT KNOW.

 NARAYANA one month ago
What is meant by algebra?

elementary algebra that follows the study of arithmetic is mostly occupied with operations on sets of whole and rational numbers and solving first and second order equqtons.algebra is a...

 raj kumar 4 months ago

Hello Prabhakar the part of mathematics in which letters and other general symbols are used to represent numbers and quantities in formulae and equations.

the part of mathematics in which letters and other general symbols are used to represent numbers and quantities in formulae and equations.

 T.kumar 4 months ago
May get help proving this one.

put a-x =t and we get now by writing cot in terms of sin and cos we can just take out the cos as cos(0) = 1, and hence what remains is and we know that the form oflimit x/sin(x) as x->0...

 Riddhish Bhalodia 3 months ago
Write direction ratios of the vector a = i + j − 2k and hence calculate its direction cosines?

Note that direction ratios a, b, c of a vector r = x i + yj + zk are just the respective components c, y and z of the vector. So, for the given vector, we have a = 1, b=1, c= –2. Further,...

 KUNCHAM SAMPATH 5 months ago
1.)The number of positive integer solutions of ab-24=2a is.

given ab-24=2a then, ab-2a=24 this implies a(b-2)=24 now, a=24/(b-2) as (a) is an integer then 24 is divisible by (b-2) and 24=2^3 * 3^1 then total umber of factors are (3+1)(1+1) = 8 so...

 manmath 3 months ago

given ab-24=2a then, ab-2a=24 this implies a(b-2)=24 now, a=24/(b-2) as (a) is an integer then 24 is divisible by (b-2) and 24=2^3 * 3^1 then total umber of factors are (3+1)(1+1) = 8 so...

 arun 3 months ago
View all Questions »

• Complete JEE Main/Advanced Course and Test Series
• OFFERED PRICE: R 15,000
• View Details
Get extra R 3,000 off
USE CODE: CART20

Get extra R 440 off
USE CODE: CART20

More Questions On Algebra