the sum s first n even natural numbers is given by the relation s=()
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Given, S = 420
420 = n(n+1)
420 = n²+n
n²+n-420 = 0
n²+21n-20n-420 = 0
n(n+21)-20(n+21) = 0
( n - 20 ) ( n + 21 ) = 0
n = 20 [ n+21 = 0 isn't considered as n can't be negative ]
Therefore ,n = 20 .
420 = n(n+1)
420 = n²+n
n²+n-420 = 0
n²+21n-20n-420 = 0
n(n+21)-20(n+21) = 0
( n - 20 ) ( n + 21 ) = 0
n = 20 [ n+21 = 0 isn't considered as n can't be negative ]
Therefore ,n = 20 .
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