Question

What is the value of i=

Answer 1

`\sum\limits_(t=1)^3\left(4\cdot\left((1)/(2)\right)^(t-1)\right)=4\cdot\left((1)/(2)\right)^(1-1)+4\cdot\left((1)/(2)\right)^(2-1)+4\cdot\left((1)/(2)\right)^(3-1)\\\\=4\cdot\left((1)/(2)\right)^0+4\cdot\left((1)/(2)\right)^1+4\cdot\left((1)/(2)\right)^2=4\cdot1+4\cdot(1)/(2)+4\cdot(1)/(4)\\\\=4+2+1=7\\\\Answer:\ \boxed{D.\ 7}`