Bài 1:
Ta có: m>n
\(\Leftrightarrow8m>8n\)
\(\Leftrightarrow8m-2>8n-2\)
Bài 3:
a) Ta có: 2-5x<3(2-x)
\(\Leftrightarrow2-5x< 6-3x\)
\(\Leftrightarrow2-5x-6+3x< 0\)
\(\Leftrightarrow-4-2x< 0\)
\(\Leftrightarrow2x< -4\)
hay x<-2
b) Ta có: \(\frac{5x-2}{3}\ge x+1\)
\(\Leftrightarrow\frac{5x-2}{3}-x-1\ge0\)
\(\Leftrightarrow\frac{5x-2}{3}-\frac{3x}{3}-\frac{3}{3}\ge0\)
\(\Leftrightarrow5x-2-3x-3\ge0\)
\(\Leftrightarrow2x-5\ge0\)
\(\Leftrightarrow2x\ge5\)
hay \(x\ge\frac{5}{2}\)
Bài 4:
Ta có: |x+5|=3x-2
\(\Leftrightarrow\left[{}\begin{matrix}x+5=3x-2\\x+5=2-3x\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x+5-3x+2=0\\x+5-2+3x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}-2x+7=0\\4x+3=0\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}-2x=-7\\4x=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{7}{2}\\x=\frac{-3}{4}\end{matrix}\right.\)
Vậy: \(S=\left\{\frac{7}{2};\frac{-3}{4}\right\}\)
1. Cho m > n, hãy so sánh 8m - 2 với 8n - 2
Ta có : \(m>n\)
\(\Rightarrow8m>8n\)
\(\Rightarrow8m-2>8n-2\)