3...cxd5?! 4.Bxf6 gxf6 5.Rge1+ Kf8 6.Qc3 etc.

Creating a powerful protected passed pawn.

6...Qa5 was correct. although after 7.Rd4 , preparing b2-b4, White keeps the advantage.

With the double threat of 9 Nd4 and 9 Rxa7. White is practically winning.

Removing the queen from the vulnerable d-file before White puts a rook on d1, and taking the g4-square away from his queen.

Gaining some space and preparing a future pawn storm on the queenside.

White has just a slight edge – Korchnoi.

A "mysterious" rook move, realizing that Black's only viable plan is ...b6-b5.

Some more prophylaxis in order to cover the sensitive second rank. Meanwhile, Black is just playing with one rook, since the one on f8 is tied to the defence of f5.