B1) 12,3 + 3,7 - 24,2 - 12,3 + 24,2 = 12,3 - 12,3 - 24,2 + 24,2 + 3,7 = 0 + 0 + 3,7 = 3,7
Bài 1 , Tự Làm
Bài 2 ,
\(\left|x-2\right|=5\)
\(\Leftrightarrow\orbr{\begin{cases}x-2=-5\\x-2=5\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-3\\x=7\end{cases}}}\)
b)\(2.\left|x+1\right|=3\)
\(\Leftrightarrow\left|x+1\right|=\frac{3}{2}\)
\(\Leftrightarrow\orbr{\begin{cases}x+1=-\frac{3}{2}\\x+1=\frac{3}{2}\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=-\frac{5}{2}\\x=\frac{1}{2}\end{cases}}\)
B2)
\(|x-2|=5\)
\(\Leftrightarrow\) x - 2 = \(\mp5\)
\(\Leftrightarrow\)\(\orbr{\begin{cases}x-2=5\\x-2=-5\end{cases}}\)\(\Leftrightarrow\)\(\orbr{\begin{cases}x=5+2\\x=-5+2\end{cases}}\)\(\Leftrightarrow\)\(\orbr{\begin{cases}x=7\\x=-3\end{cases}}\)
Vậy x = 7 , x = -3
b) \(2.|x+1|=3\)
\(\Leftrightarrow\)\(|x+1|=\frac{3}{2}\)
\(\Leftrightarrow\)\(x+1=\mp\frac{3}{2}\)
\(\Leftrightarrow\)\(\orbr{\begin{cases}x+1=\frac{3}{2}\\x+1=\frac{-3}{2}\end{cases}}\)\(\Leftrightarrow\)\(\orbr{\begin{cases}x=\frac{3}{2}-1\\x=\frac{-3}{2}-1\end{cases}}\)\(\Leftrightarrow\)\(\orbr{\begin{cases}x=\frac{1}{2}\\x=\frac{-5}{2}\end{cases}}\)
Vậy x = \(\frac{1}{2}\) , x = \(\frac{-5}{2}\)
c) \(|x\times2|=0\)
\(\Leftrightarrow\) \(x\times2=0\)
\(\Leftrightarrow\) \(x=0\)
Vậy x = 0