Which reason best explains why the author includes dialogue in the book

Consider the quadratic equation ax^2+bx+5=0,where a, b and c are rational numbers and the quadratic has two distinct zeros. if one zero is irrational what is the other zero?

Read the excerpt from "the most dangerous game." again rainsford lifted the heavy knocker, and let it fall. the door opened then, opened as suddenly as if it were on a spring, and rainsford stood blinking in the river of glaring gold light that poured out. the first thing rainsford's eyes discerned was the largest man rainsford had ever seen—a gigantic creature, solidly made and black bearded to the waist. in his hand the man held a long-barreled revolver, and he was pointing it straight at rainsford's heart. the details of this excerpt show that rainsford sees ivan as a(n) individual.

Read the excerpt from the common sense of bicycling: bicycling for ladies. the bicycle is capable of such high speed that there is a strong temptation to ride so fast as to cause over exertion or excessive perspiration. on the other hand some people ride too slow, causing a zigzag and uncertain movement. while exercising reasonable caution, be a fearless rider. when you come to a steep hill, if the road is clear, let it go as fast as it will. if you rid yourself of that ghost of fear, coasting is one of the greatest delights of cycling. which is the best paraphrase of the text?