2根号7-根号7/2+8/3根号7
=(2-1/2+8/3)√7
=25/3√7
(-根号3)^2+3根号3*根号18
=3+3√54
=3+6√6
(2-根号5)^2-(2+根号5)^2
=(2-√5+2+√5)(2-√5-2-√5)
=4x(-2√5)
=-8√5
5^1/3*5^-2÷根号5
=5^1/3*5^-2*5^-1/2
=5^(1/3-2-1/2)
=5^-13/6
(3^1/2+5^1/2)^2
=(√3+√5)²
=3+2√15+5
=8+2√15