2. write a function to create a vector x is from 2 to 4.5 (2 x 4.5) with incremental value 0.5, vector y = [x; x.^3], then save matrix y into a text file ex1-p4.txt, so that in this text file,

1. value x is formatted with decimal notation, and keep two digits after decimal point;
2. value x.^3 will displayed with exponential notation and keep three digits after decimal points;
3. each line only displays one x and x.^3, there is three spaces between x and x.^3