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1、6√15/(3√2+2√3)

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1、6√15/(3√2+2√3)
2、(5√3-3√6)/(3√3+2√6)
3、(1/√3+√2)+(1/√2-1)-2/√3+1
4、(1/a√9a³-√b³/3b²)-(2a√1/4a -b√25/b³)
5、已知x=1/√5-2,求x²-4x-1的值
1、6√15/(3√2+2√3)
1.6√15/(3√2+2√3)
= 6√15(3√2-2√3)/(3√2+2√3)(3√2-2√3)
=(18√30-36√5)/(18-12)
=(18√30-36√5)/6
=3√30-6√5
2.(5√3-3√6)/(3√3+2√6)
= (5√3-3√6)(3√3-2√6)/(3√3+2√6)(3√3-2√6)
=(45-30√2-27√2+36)/(27-24)
=(81-57√2)/3
=27-19√2
3.(1/√3+√2)+(1/√2-1)-2/√3+1
= √3/3+√2+√2/2-1-2√3/3+1
=3√2/2-√3/3
4.(1/(a√(9a³))-√b³/(3b²))-(2a√(1/4a) -b√(25/b³)) (这道题不知道那些在分子上哪些在分母上)
=√a/3a³-√b/3b-√a-5√b/b
=√a(1-1/3a³)-√b(1/3b-15/3b)
=√a(1-1/3a³)-16√b/3b
5.x²-4x-1=(x+2)²-8x-5
=(1/√5)²-8(1/√5-2)-5
=1/5-8√5/5+16-5
=56/5-8√5/5