請問這四題怎麼算,看了詳解還是不會求大大教!拜託了! 上面有亂寫的字 別管XDDD?

2018-01-02 8:53 pm

回答 (2)

2018-01-05 4:10 pm
✔ 最佳答案
(1)
a³ˣ + a⁻³ˣ   (aˣ)³ + (aˣ)⁻³
-------------- = -------------------
aˣ + a⁻ˣ    aˣ + a⁻ˣ

       (aˣ + a⁻ˣ)[(aˣ)² - (aˣ)(a⁻ˣ) + (aˣ)⁻²]
     = -------------------------------------------- - - - - - - - - -→ 公式 : a³ + b³ = (a+b) (a² - ab + b²)
           aˣ + a⁻ˣ

     = a²ˣ - 1 + a⁻²ˣ
     = 3 - 1 + 1/a²ˣ
     = 2 + 1/3
     = 7/3
~~~~~~~~~~~~~~~~~~~ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ~~~~~~~~~~~~~~~~~~~
(2)
a³ˣ - a⁻³ˣ   (aˣ)³ - (aˣ)⁻³
-------------- = -------------------
aˣ - a⁻ˣ    aˣ - a⁻ˣ

       (aˣ - a⁻ˣ)[(aˣ)² + (aˣ)(a⁻ˣ) + (aˣ)⁻²]
     = -------------------------------------------- - - - - - - - - -→ 公式 : a³ - b³ = (a-b) (a² + ab + b²)
           aˣ - a⁻ˣ

     = a²ˣ + 1 + a⁻²ˣ
     = 2 + 1 + 1/a²ˣ
     = 3 + 1/2
     = 7/2
(3)
 (aˣ + a⁻ˣ)² = (aˣ)² + 2(aˣ)(a⁻ˣ) + (a⁻ˣ)²
 =>   3² = a²ˣ + 2 + a⁻²ˣ
 => a²ˣ + a⁻²ˣ = 7

 a³ˣ + a⁻³ˣ   (aˣ)³ + (aˣ)⁻³
∴ -------------- = -------------------
 a²ˣ + a⁻²ˣ     7

       (aˣ + a⁻ˣ)[(aˣ)² - (aˣ)(a⁻ˣ) + (aˣ)⁻²]
     = ----------------------------------------... - - - - - - - - -→ 公式 : a³ + b³ = (a-b) (a² - ab + b²)
           7
 
       3 (a²ˣ - 1 + a⁻²ˣ)
     = ------------------------
         7
請等等 ......     


   
2018-01-03 2:06 am
1/a^3=1除以a^3
a^0=1
=a^0除以a^3
=a^(0-3)
=a^-3=1/a^3


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