How does Harry get the memory from Slughorn in the book?

Harry uses a combination of alcohol and guilt, invoking his mother’s memory and playing on Slughorn’s admitted fondness for her, miraculously managing to get Slughorn to give up the true memory. Ironically, Harry does this by using the Felix Felicis potion Slughorn himself made and gave to Harry as a reward.

Did Slughorn help Voldemort?

Slughorn’s impressive magical abilities allowed him to survive the Battle of Hogwarts and even stand up against Voldemort himself with aid and survive the duel.

What was Slughorn hiding?

When Slughorn realised that the Dark wizard was indeed Tom, he was mortified. When Voldemort returned to Hogwarts sometime between the late 1960s and early 1970s to try and find work as the Defence Against the Dark Arts teacher, Slughorn hid in his office so that he didn’t have to meet Tom.

How did aberforth get the mirror?

History. During their years in school, James Potter and Sirius Black used a pair of two-way mirrors so they could talk to each other while they were in separate detentions. After Sirius’ death, his mirror came into the possession of Mundungus Fletcher, who sold it to Aberforth Dumbledore.

How did Dumbledore collect the untampered Slughorn memory?

In Harry Potter and the Half-Blood Prince, Chapter 17, Dumbledore and Harry are using the Pensieve to experience the vital Slughorn memory (which was tampered with), and Harry is instructed to collect the untampered memory. My question: How did Dumbledore collect the tampered one in the first place? In that same chapter:

Why does Dumbledore order Harry to retrieve the memory about Voldemort?

In Harry Potter and the Half-Blood Prince, Dumbledore orders Harry to retrieve the memory about the talk with Tom Riddle/Voldemort from Slughorn. The memory is said to be needed because it contains Stack Exchange Network

Did Dumbledore know about Voldemort’s Horcruxes?

You’re quite right: Dumbledore already knew that Voldemort had created Horcruxes. Your confusion may stem from the fact that the word “Horcrux” isn’t mentioned in the altered memory, whereas it is in the book. But there’s no question that he knew about them.

How many Horcruxes does Tom Riddle have?

In the original, unaltered memory, Tom Riddle raises the possibility of splitting his soul into seven pieces – one inside himself, and six inside Horcruxes. This is indeed the exact number of Horcruxes he made (discounting Harry, who he made accidentally and is arguably not a Horcrux anyway).