(2+ √5) ²-√80=

Compute step by step:

• (2 + √5)^2 = 4 + 4√5 + 5 = 9 + 4√5
• √80 = √(16·5) = 4√5

Then (2 + √5)^2 − √80 = (9 + 4√5) − 4√5 = 9

Answer: 9