Question

1) The sum of first n natural numbers is given by S = n(n+1) . Find n if S. = 55. ​

Answer 1

Step-by-step explanation:

100(100+1) by 2

= 55 szz my answer.

Answer 2

S=2n(n+1)

For S=55(Given)

∴55=2n(n+1)

⇒110=n2+n

⇒n2+n−110=0

⇒n2+11n−10n−110=0

⇒(n+11)(n−10)=0

∵n=−ve

∴n=10