Respuesta :

bsit39123

Answer:

Step-by-step explanation:

First we find n:

Tn = a+ (n-1)d

Here,

a=1 ,Tn =57

d=2 ( difference between numbers is 2)

Now,

57 = 1 + (n-1)2

57 = 2n -1

58/2 = n

Or n = 29

Now, We find sum :

Sn = n/2 { a+Tn}

= 29/2 { 1 + 57 }

= 29/2 ( 58)

= 29 x 29

= 841

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