a) | x – 9 | $\geq$ 7 b) |x – 5 | $\leq$ 19 c) ( x – 13 ) ² $\geq$ 9 d) ( 3x + 5 )²$\leq$ 36

0 bình luận về “a) | x – 9 | $\geq$ 7 b) |x – 5 | $\leq$ 19 c) ( x – 13 ) ² $\geq$ 9 d) ( 3x + 5 )²$\leq$ 36”

1. Đáp án: a ) x ≥ 16

                b ) x ≥ 24

                c ) x ≥ 16

                d ) x ≤ $\frac{1}{3}$ 

   Giải thích các bước giải:

   a ) | x – 9 | ≥ 7

   → \(\left[ \begin{array}{l}x-9≥7\\x-9≥-7\end{array} \right.\) 

   → \(\left[ \begin{array}{l}x≥16\\x≥2\end{array} \right.\) 

   → x ≥ 16

   b ) | x – 5 | ≥ 19

   → \(\left[ \begin{array}{l}x-5≥19\\x-5≥-19\end{array} \right.\) 

   → \(\left[ \begin{array}{l}x≥24\\x≥-14\end{array} \right.\) 

   → x ≥ 24

   c ) ( x – 13 ) ² ≥ 9

   ( x – 13 ) ² ≥ $3^{2}$ 

   → x – 13 ≥ 3

   → x ≥ 16

   d ) ( 3x + 5 )² ≤ 36

   ( 3x + 5 )² ≤ $6^{2}$ 

   → 3x + 5 ≤ 6

   → 3x ≤ 1

   → x ≤ $\frac{1}{3}$ 

    

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2. `a,|x – 9| ≥ 7`

   `⇒` \(\left[ \begin{array}{l}x – 9 ≥ 7\\x – 9 ≥ -7\end{array} \right.\) 

   `⇒` \(\left[ \begin{array}{l}x≥ 7 + 9\\x≥ -7 + 9 \end{array} \right.\) 

   `⇒` \(\left[ \begin{array}{l}x≥ 16\\x≥ 2\end{array} \right.\) 

   `b, |x – 5 | ≤ 19`

   `⇒` \(\left[ \begin{array}{l}x-5≤19\\x-5≤-19\end{array} \right.\)

   `⇒` \(\left[ \begin{array}{l}x≤19+5\\x≤-19+5\end{array} \right.\) 

   `⇒` \(\left[ \begin{array}{l}x≤24\\x≤-14\end{array} \right.\) 

   `c,( x – 13 ) ² ≥ 9`

   `⇒ ( x – 13 ) ² ≥ 3²`

   `⇒ x – 13 ≥ 3`

   `⇒ x ≥ 16`

   `d, ( 3x + 5 )² ≤ 36`

   `⇒ ( 3x + 5 )² ≤ 6²`

   `⇒ 3x + 5 ≤ 6`

   `⇒ 3x ≤ 1`

   `⇒ x ≤ 1/3`

   Xin hay nhất !

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