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Consider the series 4 + 12 + 36 ... Find the sum of the first 9 terms.​

You can simplify the equation to make 4(1+3+9...) The nth term is therefore $$3^{n-1}$$ so u can substitute that into the equation so 4($$3^{n-1}+ 3^{n} + 3^{n+1}$$..). This would simplify to 4($$3^0 +3+3^2$$+$$3^3+3^4+3^5+3^6+3^7+3^8$$). By simplifying this, you can make it so 4($$2^2+6^2+18^2+42^2+81^2$$) = 4(4+36+324+2916+6561) =39364