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Why is there a 1 before the answer an adds up? I have done so many questions before, but there is no a 1.
A(n+ 1)= a+2 n.

A (n+1)-= 2 n

An-A (n-1) = 2 (n-1)

an-a(n- 1)=2^(n- 1)( 1)

a(n- 1)-a(n-2)=2^(n-2) (2)

...

...

a2 -a 1 = 2^0 (n- 1)

( 1)+(2)+...+(n- 1)

an -a 1 = 2^0+2^ 1+....+2^(n- 1)

= 2^(n- 1) - 1

An-1= 2 (n-1)-1

An = 2 (n-1)