Question

sum of first 9 nstural odd numbers if Sn= n×n
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Answer 1

Answer:

so is then 9×9=81

Step-by-step explanation:

sn =n/2(first term+ last term)

=9/2 ( 1+17)

= 9/2(18)

=9×9

=81

Answer 2

Answer:

81

Step-by-step explanation:

Sn=n/2[2a+(n-1)d]

S9=9/2[2×1+(9-1)2]

S9=9/2[2+8×2]

S9=9/2[18]

S9=9 ×9

S9=81

so,answer is 81.