根号1至根号20的平方根和立方根还有平方数,比如2的平方为4,3为9这样的.保留小数点后三位有效数字,比如1.732这样的.（不会的请不要乱说,以前提过,白浪费5分）

√0 = 0（表示根号0等于0,下同）
√1 = 1
√2 = 1.4142135623731
√3 = 1.73205080756888
√4 = 2
√5 = 2.23606797749979
√6 = 2.44948974278318
√7 = 2.64575131106459
√8 = 2.82842712474619
√9 = 3
√10 = 3.16227766016838
√11 = 3.3166247903554
√12 = 3.46410161513775
√13 = 3.60555127546399
√14 = 3.74165738677394
√15 = 3.87298334620742
√16 = 4
√17 = 4.12310562561766
√18 = 4.24264068711928
√19 = 4.35889894354067
√20 = 4.47213595499958
立方根
3√0 = 0
3√1 = 1
3√2 = 1.25992104989487
3√3 = 1.44224957030741
3√4 = 1.5874010519682
3√5 = 1.7099759466767
3√6 = 1.81712059283214
3√7 = 1.91293118277239
3√8 = 2
3√9 = 2.0800838230519
3√10 = 2.15443469003188
3√11 = 2.22398009056932
3√12 = 2.28942848510666
3√13 = 2.35133468772076
3√14 = 2.41014226417523
3√15 = 2.46621207433047
3√16 = 2.51984209978975
3√17 = 2.57128159065824
3√18 = 2.6207413942089
3√19 = 2.66840164872194
3√20 = 2.71441