(2căn3-căn5+căn27)(căn75+căn5)
=30-5căn15+45+2căn15-5+3căn5
=căn15(-5+2+3)+30+45-5
=70

2--I,Trắc nghiệm 

1. b
2. d
3. c
4. a

2--Tự luận
1,√48-2√24/3-2√(1/3)-√243+2√108
=4√3-4√6/3-2/3.√3-9√3+12√3
=(4√6+19√3)/3
b,((6-2√3)/(√3-1)+3/(√3+3)).4/(√3+1)
=((2√3(√3-1)/(√3-1)+√3/(√3+1)).4/(√3+1)
=8√3/(√3+1)+4√3/(√3+1)^2
=(24+8√3+4√3)/(2√3+4)
=6(2√3+4)/(2√3+4)
=6