a, |-1+5x|=8-x b, |-2x+1|=x+3 c, |-2-5x|=-4x+7 can gap lém

0 bình luận về “a, |-1+5x|=8-x b, |-2x+1|=x+3 c, |-2-5x|=-4x+7 can gap lém”

1. Đáp án:

    

   Giải thích các bước giải:

   `a, |-1+5x|=8-x`

   `ĐK:8-x=0=>x<=8`

   ⇔ \(\left[ \begin{array}{l}-1+5x=8-x\\-1+5x=-8+x\end{array} \right.\)

   ⇔\(\left[ \begin{array}{l}5x+x=8+1\\5x-x=-8+1\end{array} \right.\)

   ⇔\(\left[ \begin{array}{l}x=\dfrac{3}{2}(tm)\\x=-\dfrac{7}{4}(tm)\end{array} \right.\) 

   `b, |-2x+1|=x+3`

   `ĐK:x>=-3`

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

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

   ⇔\(\left[ \begin{array}{l}x=-\dfrac{2}{3}(tm)\\x=4(tm)\end{array} \right.\) 

   `c, |-2-5x|=-4x+7`

   `ĐK:-4x+7>=0`

   `<=>x<=7/4`

   ⇔ \(\left[ \begin{array}{l}-2-5x=-4x+7\\-2-5x=4x-7\end{array} \right.\)

   ⇔\(\left[ \begin{array}{l}-5x+4x=7+2\\-5x-4x=-7+2\end{array} \right.\)

   ⇔\(\left[ \begin{array}{l}x=-9(Loại)\\x=\dfrac{5}{9}(tm)\end{array} \right.\) 

   Trả lời