3.已知立方√0.214≈0.5981,立方√2.14≈1.289,立方√21.4≈2.776,则立方√0.00214≈.14.若立方√2x-5和立方√5-3y互为相反数,则y分之x=.5.已知M=（在立方那上面的）m-n-1√m+3是m+3的算数平方根,N=（在立

Question

3.已知立方√0.214≈0.5981,立方√2.14≈1.289,立方√21.4≈2.776,则立方√0.00214≈ .14.若立方√2x-5和立方√5-3y互为相反数,则y分之x= .5.已知M=（在立方那上面的）m-n-1√m+3是m+3的算数平方根,N=（在立方那上面的）2m-4n+3√n-2是n-2的立方根,试求M-N的值.

Answer 1

第一题
立方√0.00214
=立方√(0.001*2.14)
=立方√0.001 * 立方√(2.14
≈0.1*1.289
=0.1289
第二题
立方√2x-5和立方√5-3y互为相反数
³√2x-5 + ³√5-3y =0³
³√2x-5 = -³√5-3y
2x-5 = -5+3y
x/y = 3/2
第三题
m-n-1 ＝2
2m-4n+3 ＝3
解之 m =6 n=3
代入得到 M＝3 N＝1
M-N＝2