Question 64778
4R^2-25S^2=(2R+5S)(2R-5S)
2R^2+3RS-20S^2=(2R-5S)(R+4S)
(2R+5S)(2R-5S)/(25-5S)(R+S) CANCEL OUT THE COMMON FACTORS (2R-5S) WE HAVE LEFT
(2R+5S)/(R+S)