a) \(\left|2x\right|-\left|-2,5\right|=\left|-7,5\right|\)
\(\Leftrightarrow\left|2x\right|-2,5=7,5\)
\(\Leftrightarrow\left|2x\right|=10\)
\(\Leftrightarrow\begin{cases}x\ge0\\2x=10\end{cases}\) hoặc \(\begin{cases}x< 0\\2x=-10\end{cases}\)
\(\Leftrightarrow\begin{cases}x\ge0\\x=5\left(tm\right)\end{cases}\) hoặc \(\begin{cases}x< 0\\x=-5\left(tm\right)\end{cases}\)
Vậy x={5;-5}
b)\(\left|3x\right|\cdot\left|-3,5\right|=\left|-2,8\right|\)
\(\Leftrightarrow\left|3x\right|\cdot3,5=2,8\)
\(\Leftrightarrow\left|3x\right|=\frac{4}{5}\)
\(\Leftrightarrow\begin{cases}x\ge0\\3x=\frac{4}{5}\end{cases}\) hoặc \(\begin{cases}x< 0\\3x=-\frac{4}{5}\end{cases}\)
\(\Leftrightarrow\begin{cases}x\ge0\\x=\frac{4}{15}\end{cases}\) hoặc \(\begin{cases}x< 0\\x=-\frac{4}{15}\end{cases}\)
Vậy x={4/15;-4/15}
c) \(\left(3x-5\right)\left(\frac{3}{2}x+2\right)\left(0,5x-10\right)=0\)
\(\Leftrightarrow\left[\begin{array}{nghiempt}3x-5=0\\\frac{3}{2}x+2=0\\0,5x-10=0\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}x=\frac{5}{3}\\x=-\frac{4}{3}\\x=20\end{array}\right.\)
a)|2x|-|-2,5|=|-7,5|
|2x|-2,5=7,5
|2x|=10
\(\Rightarrow\left[\begin{array}{nghiempt}2x=10\\2x=-10\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=5\\x=-5\end{array}\right.\)
Vậy x=5;-5
b)|3x|.|-3,5|=|-2,8|
|3x|.3,5=2,8
|3x|=0,8
\(\Rightarrow\left[\begin{array}{nghiempt}3x=0,8\\3x=-0,8\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=\frac{4}{15}\\x=-\frac{4}{15}\end{array}\right.\)
Vậy \(x=\frac{4}{15};-\frac{4}{15}\)
c, ( 3x - 5 ) . ( \(\frac{3}{2}x\) + 2 ) . ( 0,5x - 10 ) = 0
\(\left(3x^2+6x-\frac{15}{2}x-10\right)\left(0,5x-10\right)=0\)
\(\left(3x^2-\frac{3}{2}x-10\right)\left(0,5x-10\right)=0\)
\(1,5x^3-0,75x^2-5x-30x^2+15x+100=0\)
\(1,5x^3-30,75x^2+10x+100=0\)
\(1,5x^3-1,5x^2.20,5+10x+100=0\)
\(1,5x^2.\left(x-20,5\right)+10.\left(x+10\right)=0\)
Đến đây thì mk .......
