Question

Help? Anyone have and idea?

Answer 1

`y=a\cdot b^x\quad,\quad b>0`

a)

`128=2 b^3\\ b^3=64\\ b=4\\\\ y=2\cdot4^x`


b)

`4=a\cdot b^0\\ 1=a\cdot b^2\\\\ a=4\\ 1=a\cdot b^2\\\\ 1=4\cdot b^2\\ b^2=(1)/(4)\\ b=(1)/(2) \vee b=-(1)/(2)\\ -(1)/(2)<0 \Rightarrow b=(1)/(2)\\\\ y=4\cdot \left((1)/(2)\right)^x`