解1题
2√18÷3√2
=(2×3√2)÷3√2
=2
2题
(√2+1)÷(√2-1)
=[(√2+1)²]÷[(√2-1)(√2+1)]
=(2+2√2+1)÷(2-1)
=3+2√2
3题:
3√2×(-√14)/6×1/√7
=3√2×(-√14)/6×(√7)/7
=-(3×√(2×14×7)/(6×7)
=-(3×14)/(6×7)
=-42/42
=-1
4题
√18÷(√8×√3)
=√[18÷(8×3)]
=√(18/24)
=√(3/4)
=√[(4×3)/(4×4)]
=2√3/4
=√3/2
第二个做错了。第四个等于√3/2