Who said the following lines and why?
a. "is she a Capulet? O dear account, my life is my foe's debt."
b. b. "My only love sprung from my only hate Too early seen unknown and known too late."
At the Capulet's ball, Romeo asks the nurse about Juliet's identity and he is distraught at hearing that she is a Capulet, sworn enemy to the Montagues, Romeo's family. There exists an age-old feud between the two houses.
Romeo uses an accounting metaphor: by mentioning a "dear account" he suggests that there is a high price to pay for being in love with one's enemy.
"My life is my foe's debt" implies that Romeo's life is now in his enemy's hands. Whatever account there is to settle will be paid for with his life - this foreshadows his tragic death later. Furthermore, it also suggests that his life will be controlled by his enemy. He will forever be at Juliet's command for he loves her. She will be master of his fate and the paradox is that she is, at once, also his enemy being the daughter of his family's sworn opposition. Furthermore, his enemy, in this sense, Juliet, owes him his life - she gives him a reason to live for he is overwhelmed by his love for her.
The nurse later tells Juliet who Romeo is and she too, overwhelmed by the information, comments about her 'only love' which has found its source in her 'only hate'. This means that the one person whom she truly loves is also a member of the one family that she has been taught to hate. She loves no other and she hates no one else. This once again presents a paradox: how does one love and hate the same person at the same time?
Juliet expresses her dismay by observing that she had seen (or fallen in love with Romeo) "too early", i.e. before she knew who he really was and she only discovered his true identity when it was "too late". Her love for him could not be undone despite the fact that he was supposed to be a member of her family's sworn enemy.
What these two lines are is the responses of Romeo and Juliet, respectively, when they find out who it is that they have fallen in love with. These lines are spoken at the ball after the two of them have each found out who the other is.
Romeo's line means that his enemy now controls his life. This is because he believes that he can't live without Juliet and she is controlled by Lord Capulet.
Juliet's line is saying that she wishes she would have known beforehand who Romeo was. She has found out too late that he is an enemy -- too late because she's already in love.
the first quote is by romeo and its cause he's fallen in love with a capulet which is his family's enemy so his debt is to his enemy