f.5數學二問

先計上半部
(1/a+1/b)
=b/ab + a/ab
=a+b/ab

下半部
1/a3 + 1/b3
=b/3ab + a/3ab
=a+b/3ab

綜合~~
(a+b/ab) / (a+b)/3ab
=3ab/ab
=3

我想知(1/a3+1/b3)係唔係(1/a^3+1/b^3)???

if (1/a3+1/b3)

(1/a+1/b) / (1/a3+1/b3)
=(b/ab + a/ab) / (b/3ab + a/3ab)
=(a+b/ab) / (a+b)/3ab
=3ab/ab
=3

if(1/a^3+1/b^3)

(1/a3+1/b3) / (1/a^3+1/b^3)
=(1/a3+1/b3) / [(1/a^3+1/b^3)*(1/a^2 -1/ab + 1/b^2)]
=1 / (1/a^2 - 1/ab + 1/b^2)

formula: a^3+b^3=(a+b)(a^2-ab+b^2), ^ 係次方