a, 4x + 3.13 = 15 b,23 + ( 2x – 1)^2 = (-2)^4 .2

0 bình luận về “a, 4x + 3.13 = 15 b,23 + ( 2x – 1)^2 = (-2)^4 .2”

1. Đáp án:

   `a,4x+3.13=15`

   `\to4x+39=15`

   `\to4x=15-39`

   `\to4x=-24`

   `\tox=-6`

   Vậy `x=-6`

   `b,23+(2x-1)^2=(-2)^4 . 2`

   `\to23+(2x-1)^2=32`

   `\to(2x-1)^2=32-23`

   `\to(2x-1)^2=9`

   `\to(2x-1)^2=3^2`

   `\to` \(\left[ \begin{array}{l}2x-1=3\\2x-1=-3\end{array} \right.\) `\to` \(\left[ \begin{array}{l}x=2\\x=-1\end{array} \right.\) 

   Vậy `x\in{-1;2}`

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2. Đáp án:

   ` a ) x = -6,5`

   `b )` \(\left[ \begin{array}{l}x+1 = 0⇒x = -1\\x-2=0 ⇒x=2\end{array} \right.\) 

   Giải thích các bước giải:

   ` a ) 4x + 3 . 13 = 13`

         `⇔4x + 39 = 13`

         `⇔4x = -26`

         `⇔x = -( 26 )/4 = -6,5`

   `b ) 23 + ( 2x – 1 )^2 = ( – 2 )^4 . 2`

       `⇔23 + 4x^2 – 4x + 1 = 32`

       `⇔ 4x^2 – 4x – 8 = 0`

       `⇔ x^2 – x – 2 = 0`

       `⇔x^2 + x – 2x – 2 = 0`

       `⇔x ( x + 1 ) – 2 ( x + 1 ) = 0`

       `⇔( x + 1 ) ( x – 2 ) = 0`

   `⇒` \(\left[ \begin{array}{l}x+1 = 0⇒x = -1\\x-2=0 ⇒x=2\end{array} \right.\) 

        

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