summation

find 1.22+2.32+3.42+.....to n terms

11 Answers

62
Lokesh Verma ·

Hint: 1=2-1

2=3-1

3 = 4-1

Now try..

1
ut10 ·

thanks bhaiya.
2 : 14+24+34+44+.......

62
Lokesh Verma ·

2nd one the first proof is quite boring...

It goes like this:

15-05 = 14
25-15 = 24+23+22+2+1
35-25 = 34+2.33+2232+....

....

....

...

Then add..

1
student ·

apply direct summation

n(n+1)2=n(n2+2n+1)

Σn3+2Σn2+Σn

62
Lokesh Verma ·

how does that help? I din get ur proof RPF?

1
student ·

second one same as bhaiya

Σ(n5-(n-1)5)+10Σn3-10Σn2+5Σn-15=Σn4

Σn4=(n5)+10Σn3-10Σn2+5Σn-15

1
Sridhar M ·

He found the nth term and the resulting summation is found.

1
student ·

i think bhaiya thought i posted solution for second one

1
ut10 ·

find the sum of the series 12 ,40 ,90 ,168 ,280 ,432,.................

62
Lokesh Verma ·

See these:

2x6
4.10
6. 15
8. 21
10.28
12.36

Now try.

1
ut10 ·

thanks bhaiya gr8
getting Tn= 2n * (n2+5n+6)/2
by multiplying and then doing summation getting right solution.

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