Is there a mate in two moves for white?

Question

How is this a mate in two? I can't see it.

[fen "k4r2/1rQ1b1p1/2Rp1n2/1p2p2p/P7/1P3PBq/5P1P/4K2R w - - 0 1"]

Answer 1

After Ra6+ black's only possible move is Ra7 when white has Qxa7# and Rxa7# both of which are mate

[fen "k4r2/1rQ1b1p1/2Rp1n2/1p2p2p/P7/1P3PBq/5P1P/4K2R w - - 0 1"]

1. Ra6+ Ra7 2. Qxa7# (2. Rxa7#)

Answer 2

In a puzzle like this, first look at the ways in which white can give Check. That will force black to respond to the check which dramatically reduces the number of possibilities.

White has five possible checks with the queen, but none of them work out. If white gives check on the back rank, black can simply capture it with their rook. If white captures the black rook on B7 with their queen then black can capture it with their king. If white gives check with the queen on A5 then black can either block with their rook or move the king. In either case white lacks a good follow-up.

However, white also has a check with the rook. Black doesn't have any pieces that can capture white's rook and can't move their king since all the squares it could move to are covered. So they are forced to block with their rook.

That leaves black's rook under double attack, either the rook or the queen can capture it to deliver checkmate.