1, ∫a is the fractional part of √3, and b is the integer part of √5.

∴ a=√3- 1，b=2

∴ a+b= 1+√3

2. The side length is √(3×2.5×30)=√225= 15cm.

3. Original surface area: (12× 9+12× 2+9× 2 )× 2 = 300 cm?

The side length of the cube after processing: (12×9×2)=6cm under the number of cubic roots.

Surface area of cube: 6×6×6=2 16cm?

∴ Surface area decreased by 300-2 16=84cm?