In Pride and Prejudice, why and how have Elizabeth and Mr. Darcy changed in chapters 35-50?
In Chapter 35 of Pride and Prejudice, Elizabeth receives Mr. Darcy's letter following his disastrous marriage proposal. In it he clearly states that he is writing the letter because his "character required it to be written and read." This informs the reader that Mr. Darcy's essential character has not been and will not be changed. However, we learn as time and events progress that he does change some errors of thought and perception that have blinded him in proud misconceptions.
Elizabeth's reaction to the letter, detailed in Chapter 36, starts out with her usual accusation of "pride and insolence" coming from Mr. Darcy. After reading and rereading Darcy's letter, she ends by declaring that her every sentiment and thought regarding both Darcy and Wickham--so closely tied together in the letter--has been "blind, partial, prejudiced, absurd." She declares that she has prided herself on her discernment and now finds herself horribly prejudiced. As time and events progress, Elizabeth learns how to make amends for her previous prejudice, which, she learns with horror, has enabled Wickham to compromise her own sister.
Darcy learns (Chapters 49 and 50) how to act in a genuine manner without pride or, in his turn, prejudice by hunting down the location in London of Wickham and Lydia, an effort that causes him no small pain because it puts him in close contact with people who have betray and hurt him. He then finds a way to make amends for his previous pride and prejudice by conferring with the Gardiners and by arranging an honorable and comfortably financed marriage between Wickham and Lydia.