Example 16. The sum of first n evennatural numbers is given by the rel

1.	Example 16. The sum of first n evennatural numbers is given by the relations n(n +1). Find n, if the sum is 420.
Answer» 420 = n (n + 1 ) use distributive property 400 + 20 = n^2+ n transpose 400 - n^2= n - 20 get the square root of 400 - n^2then it becomes 20 - n = n - 20 transpose 20 + 20 = n + n then add 40 = 2n then divide by 2 on each side to get the value of n n = 20

Example 16. The sum of first n evennatural numbers is given by the relations n(n +1). Find n, if the sum is 420.

Answer»

420 = n (n + 1 ) use distributive property

400 + 20 = n^2+ n transpose

400 - n^2= n - 20 get the square root of 400 - n^2then it becomes

20 - n = n - 20 transpose

20 + 20 = n + n then add

40 = 2n then divide by 2 on each side to get the value of n

n = 20