How do you simplify rational expressions

Which math sentence can be used to determine if the triangle is a right triangle?

Acertain population of bacteria demonstrates exponential growth doubles in size every 4 days. how long will it take the population to triple in size?

Can you me with this question? i'll reward *30 points i just need with this one question so that i could solve the others. * edit: i originally set up the question to reward 30 points, but for some reason i can only reward 15. if you don't get 30, then i'm sorry. i'm still kind of new to this site