All 5 Uses of

positive

in

Pride and Prejudice

Against staying longer, however, Elizabeth was positively resolved—nor did she much expect it would be asked; and fearful, on the contrary, as being considered as intruding themselves needlessly long, she urged Jane to borrow Mr. Bingley's carriage immediately, and at length it was settled that their original design of leaving Netherfield that morning should be mentioned, and the request made.
p. 58.5

positively = absolutely (used for emphasis)

As to her younger daughters, she could not take upon her to say—she could not positively answer—but she did not know of any prepossession; her eldest daughter, she must just mention—she felt it incumbent on her to hint, was likely to be very soon engaged.
p. 70.3

positively = with certainty

Resignation to inevitable evils is the evil duty of us all; the peculiar duty of a young man who has been so fortunate as I have been in early preferment; and I trust I am resigned. Perhaps not the less so from feeling a doubt of my positive happiness had my fair cousin honoured me with her hand; for I have often observed that resignation is never so perfect as when the blessing denied begins to lose somewhat of its value in our estimation.
p. 112.4

positive = absolute (used for emphasis)

Nothing less than the complaisance of a courtier could have borne without anger such treatment; but Sir William's good breeding carried him through it all; and though he begged leave to be positive as to the truth of his information, he listened to all their impertinence with the most forbearing courtesy.
p. 124.5

positive = certain

The fishing scheme had been renewed the day before, and a positive engagement made of his meeting some of the gentlemen at Pemberley before noon.
p. 254.5 *

Definitions:

(1) (positive as in: I'm absolutely positive!)
certain (having no doubt; or used for emphasis)
(2) (positive as in: had a positive effect)
good or beneficial
(3) (positive as in: positive feedback from my boss)
approval or agreement
(4) (positive as in: a positive attitude)
optimistic (expecting or focusing good things); or agreeable
(5) (positive as in: The test came back positive.)
found a condition or substance to be present
(6) (positive as in: a positive number)
greater than zero (of a number)
(7) (meaning too rare to warrant focus)
See a comprehensive dictionary for less common meanings of positive including some in the fields of electricity, physics, chemistry, medicine, philosophy, and grammar. Note that most all senses of positive indicate that something is good or present.