Solve for a_n
a_{n}=\frac{S_{n}+4}{2}
Solve for S_n
S_{n}=2\left(a_{n}-2\right)
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2a_{n}-4=S_{n}
Swap sides so that all variable terms are on the left hand side.
2a_{n}=S_{n}+4
Add 4 to both sides.
\frac{2a_{n}}{2}=\frac{S_{n}+4}{2}
Divide both sides by 2.
a_{n}=\frac{S_{n}+4}{2}
Dividing by 2 undoes the multiplication by 2.
a_{n}=\frac{S_{n}}{2}+2
Divide S_{n}+4 by 2.
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