a) -x × (8+ x)=0
b)|x|-| -x+3| =7 với 0
a) -x × (8+ x)=0
b)|x|-| -x+3| =7 với 0
By Rylee
By Rylee
Đáp án:
a) \(\left[ \begin{array}{l}
x = 0\\
x = – 8
\end{array} \right.\)
b) \(x \in \emptyset \)
c) \(\left[ \begin{array}{l}
x = 0\\
x = 5\\
x = 10\\
x = 15\\
….
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a) – x.\left( {8 + x} \right) = 0\\
\to \left[ \begin{array}{l}
x = 0\\
x = – 8
\end{array} \right.\\
b)\left| x \right| – \left| { – x + 3} \right| = 7\\
\to x – \left( {x – 3} \right) = 7\left( {do:0 < x < 3} \right)\\
\to x – x + 3 = 7\\
\to 3 = 7\left( {KTM} \right)\\
\to x \in \emptyset \\
c)x + 5 \vdots 5\\
\to x + 5 \in B\left( 5 \right)\\
\to \left[ \begin{array}{l}
x + 5 = 5\\
x + 5 = 10\\
x + 5 = 15\\
x + 5 = 20\\
….
\end{array} \right. \to \left[ \begin{array}{l}
x = 0\\
x = 5\\
x = 10\\
x = 15\\
….
\end{array} \right.
\end{array}\)