-11+r=-18. how to solve ?

If the ratio of sum of the first m and n terms of an ap is m2 : n2 , show that the ratio of its mth and nth terms is (2m − 1) : (2n − 1).

The customer price index(cpi), which measures the cost of a typical package of customer goods,was 208.8 in 2011 and 244.1 in 2016.let x=11 corresponding to the year 2011 an estimate to cpi into 2013 and 2014. assume that the data can be modeled by a straight line and the trend to continue idenfinitely.use data points to find such a line and then estimate the requested quantities

Which of the functions below could have created this graph?