Toán Lớp 8: giải các pt sau
b, l 7-2x l +7=2x
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Toán Lớp 8: giải các pt sau
b, l 7-2x l +7=2x
Comments ( 1 )
|7-2x|+7=2x
<=>|7-2x|=2x-7
<=>\(\left[ \begin{array}{l}7-2x=2x-7\\7-2x=7-2x\end{array} \right.\)
<=>\(\left[ \begin{array}{l}2x+2x=7+7\\2x=2x\end{array} \right.\)
<=>\(\left[ \begin{array}{l}4x=14\\x=x (Tm ∀x≤\dfrac72)\end{array} \right.\)
<=>\(\left[ \begin{array}{l}x=\dfrac72 (Tm)\\x=x (Tm ∀x≤\dfrac72)\end{array} \right.\)
Vậy : x<=7/2 là nghiệm của phương trình