2. simplify (1/a+1/b)除以(1/a3+1/b3)
詳細步驟..唔該哂..!!!!@@
f.5數學二問
2007-11-05 9:38 pm
回答 (2)
2007-11-05 9:47 pm
✔ 最佳答案
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
2007-11-05 11:03 pm
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
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
參考: 自己做
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