Concept:Recognize that the numerator is a multiple of the derivative of the denominator and use ∫f(x)f′(x)dx=log∣f(x)∣+c.Explanation:Let f(x)=x15+15x.Then f′(x)=15x14+15xlog15.Also, log225=log(152)=2log15.So the numerator becomes 30x14+15x(2log15)=2(15x14+15xlog15).Thus numerator =2f′(x).The integral is I=∫f(x)2f′(x)dx.Using the standard formula, I=2log∣f(x)∣+c.This can be written as I=log(x15+15x)2+c.Answer:Option C: log(x15+15x)2+c, where c is the constant of integration.