m=(-√3)/3乘以(-2√21)则有A.5﹤m﹤6B.4﹤m﹤5C.-5﹤m﹤-4D.-6﹤m﹤-5并告知为什么

Question

m=(-√3)/3 乘以(-2√21)则有A.5﹤m﹤6 B.4﹤m﹤5 C.-5﹤m﹤-4 D.-6﹤m﹤-5 并告知为什么

Answer 1

m=2√(21*3)/3
=2√63/3
=2*3√7/3
=2√7
则m²=28
则25