In a village, the cases of a particular infectious disease have been exponentially decreasing at a rate of 95% per year since the people started receiving the vaccine. If there were 200 cases in the village to start with predict the number of cases after two years

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.