Question

The sum of the Series 1.3.5 + 2.5.8 +3.7.11 + .......upto 'n' terms is
​

Answer 1

Step-by-step explanation:

Given series is,

1.3.5 + 2.5.8 + 3.7.11 + ⋯ + (2 + 1) (3 + 2)

So, = (2 + 1)(3 + 2) = [6

2 + 4 + 3 + 2]

= 6

3 + 7

2 + 2

Now, sum = 6Σ

3 + 7Σ

2 + 2Σ

= 6 [

1

2

( + 1)]

−2

+ 7 [

1

6

( + 1)(2 + 1)] + 2 [

1

2

( + 1)]

=

1

6

( + 1)[9

2 + 9 + 14 + 7 + 6]

=

1

6

( + 1)[9

2 + 9 + 14 + 7 + 6]

=

(+1) (9

2+23+13)

6

.

Embibe’s Approach – Put = 2 and see which answer is giving 3

1

+

5

5

= 4.

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Answer 2

Step-by-step explanation:

8. Which among the following is an earthquake and typhoon proof bridge?

a) Millau viaduct

b) Poughkeepsie

c) Qingdao-Haiwan Road bridge

c) Danyang-kunshan Grand Bridge

rents called?