(3+1/3)(3ˆ2+1/3ˆ2)(3ˆ4+1/3ˆ4)(3ˆ8+1/3ˆ8)(3ˆ16+1/3ˆ16)
问题描述:
(3+1/3)(3ˆ2+1/3ˆ2)(3ˆ4+1/3ˆ4)(3ˆ8+1/3ˆ8)(3ˆ16+1/3ˆ16)
答
(3+1/3)(3ˆ2+1/3ˆ2)(3ˆ4+1/3ˆ4)(3ˆ8+1/3ˆ8)(3ˆ16+1/3ˆ16)
=(3/8)(3-1/3)(3+1/3)(3ˆ2+1/3ˆ2)(3ˆ4+1/3ˆ4)(3ˆ8+1/3ˆ8)(3ˆ16+1/3ˆ16)
=(3/8)(3ˆ2-1/3ˆ2)(3ˆ4+1/3ˆ4)(3ˆ8+1/3ˆ8)(3ˆ16+1/3ˆ16)
=(3/8)(3ˆ4-1/3ˆ4)(3ˆ8+1/3ˆ8)(3ˆ16+1/3ˆ16)
=(3/8)(3ˆ8-1/3ˆ8)(3ˆ16+1/3ˆ16)
=(3/8)(3ˆ16-1/3ˆ16).
本题似乎没太大的意义!就直接算?这不是直接算呀,主要是联想到平方差公式的应用,从而先乘以(3-1/3)/(3-1/3)=(3/8)(3-1/3)。