a) 216: ( 2 – x ) mũ 3 = 2 mũ 3 b) ( 2x mũ 3 + 12 ) – ( x mũ 3 + 5 ) = 15 c) ( 4 + 3x mũ 2 ) – ( x mũ 2 – 1 ) = 7

0 thoughts on “a) 216: ( 2 – x ) mũ 3 = 2 mũ 3 b) ( 2x mũ 3 + 12 ) – ( x mũ 3 + 5 ) = 15 c) ( 4 + 3x mũ 2 ) – ( x mũ 2 – 1 ) = 7”

1. `a)216:(2−x)^3=23`

   `⇒216:(2−x)^3=8`

   `⇒(2−x)^3=27`

   `⇒(2−x)^3=3^3`

   `⇒2−x=3`

   `⇒x=−1`

   `b) (2x^3+12)-(x^3+5)=15`

   `=> 2x^3+12-x^3-5=15`

   `=> x^3+7=15`

   `=> x^3=15-7=8`

   `=> x^3=2^3`

   `=> x=2`

   `c) (4+3x^2)-(x^2-1)=7`

   `=> 4+3x^2-x^2+1=7`

   `=> 5+2x^2=7`

   `=> 2x^2=7-5=2`

   `=> x^2=1`

   `=> x=±1`

    

   Reply

2. Đáp án:

    b. x=3

   Giải thích các bước giải:

   \(\begin{array}{l}
   a.DK:x \ne 2\\
   216:{\left( {2 – x} \right)^3} = {2^3}\\
    \to 216:{\left( {2 – x} \right)^3} = 8\\
    \to {\left( {2 – x} \right)^3} = 27\\
    \to {\left( {2 – x} \right)^3} = {3^3}\\
    \to 2 – x = 3\\
    \to x =  – 1\\
   b.\left( {2{x^3} + 12} \right) – \left( {{x^3} + 5} \right) = 15\\
    \to {x^3} + 7 = 15\\
    \to {x^3} = 8\\
    \to {x^3} = {2^3}\\
    \to x = 3\\
   c.4 + 3{x^2} – {x^2} + 1 = 7\\
    \to 2{x^2} + 5 = 7\\
    \to 2{x^2} = 2\\
    \to {x^2} = 1\\
    \to \left[ \begin{array}{l}
   x = 1\\
   x =  – 1
   \end{array} \right.
   \end{array}\)

   Reply