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\(-2,5+\left|3x+5\right|=-1,25\)
\(\left|3x+5\right|=-1,25-\left(-2,5\right)\)
\(\left|3x+5\right|=-1,25+2,5\)
\(\left|3x+5\right|=1,25\)
\(\Rightarrow3x+5=1,25\) hoặc \(3x+5=-1,25\)
* \(3x+5=1,25\)
\(3x=1,25-5\)
\(3x=-3,74\)
\(x=\frac{-3,74}{3}\)
\(x=-1,25\)
* \(3x+5=-1,25\)
\(3x=-1,25-5\)
\(3x=-6,25\)
\(x=\frac{-6,25}{3}\)
\(x=-2,08\)
Vậy \(x\in\left\{-1,25;-2,08\right\}\)
d. \(\left|x-\frac{2}{5}\right|+\frac{1}{2}=\frac{3}{4}\)
\(\left|x-\frac{2}{5}\right|=\frac{3}{4}-\frac{1}{2}\)
\(\left|x-\frac{2}{5}\right|=\frac{3-2}{4}\)
\(\left|x-\frac{2}{5}\right|=\frac{1}{4}\)
Vậy \(x-\frac{2}{5}=\frac{1}{4}\) hoặc \(x-\frac{2}{5}=\frac{-1}{4}\)
* \(x-\frac{2}{5}=\frac{1}{4}\)
\(x=\frac{1}{4}+\frac{2}{5}\)
\(x=\frac{5+8}{20}\)
\(x=\frac{13}{20}\)
* \(x-\frac{2}{5}=\frac{-1}{4}\)
\(x=\frac{-1}{4}+\frac{2}{5}\)
\(x=\frac{-5+8}{20}\)
\(x=\frac{3}{20}\)
Vậy \(x\in\left\{\frac{13}{20};\frac{3}{20}\right\}\)
d) |x-2/5| +1/2 = 3/4
=> |x-2/5| = 1/4
<=> x-2/5 = 1/4 hoặc x=2/5 = -1/4
<=> x=13/20 hoặc 3/20
e) 5/6 -| 2-x| = 1/3
=> |2-x|=1/2
<=> 2-x=1/2 hoặc 2-x=-1/2
<=> x=3/2 hoặc x=5/2
g) làm tương tự
\(\Leftrightarrow\left(19.75\right):x=\left(\dfrac{33}{5}-\dfrac{51}{16}\right)\cdot\dfrac{35}{6}:\dfrac{5}{2}\)
\(\Leftrightarrow19.75:x=\dfrac{637}{80}\)
hay x=1580/637
\(A=\left(\frac{1,5+1-0,75}{2,5+\frac{5}{3}-1,25}+\frac{0,375-0,3+\frac{3}{11}+\frac{3}{12}}{-0,625+0,5-\frac{5}{11}-\frac{5}{12}}\right)\div\frac{1890}{2005}+115\)
\(A=\left(\frac{3\left(0,5+\frac{1}{3}-0,25\right)}{5\left(0,5+\frac{1}{3}-0,25\right)}+\frac{3\left(0,125-0,1+\frac{1}{11}+\frac{1}{12}\right)}{-5\left(0,125-0,1+\frac{1}{11}+\frac{1}{11}\right)}\right)\div\frac{1890}{2005}+115\)
\(A=\left(\frac{3}{5}+\frac{-3}{5}\right)\div\frac{1890}{2005}+115\)
\(A=0\div\frac{1890}{2005}+115\)
\(A=115\)
P = 2005 : ( 3(0,125 - 0,1 + 1/11 + 1/12)/-5(0,125 - 0,1 + 1/11 + 1/12) * 5(0,5 + 1/3 - 0,25)/3(0,5 +1/3 - 0,25) )
P = 2005 : (-3/5 * 5/3)
P = 2005 : (-1) = -2005
Chẳng cần máy tính cũng làm ra, có khi còn nhanh hơn máy tính
\(\left(2,5-3x\right):1\dfrac{2}{3}=\left(\dfrac{8}{5}+2x\right):\left(-\dfrac{8}{17}\right)\)
\(\Rightarrow\dfrac{7,5-9x}{5}=\dfrac{-27,2-34x}{8}\)
\(\Rightarrow60-72x=-217,6-272x\)
\(\Rightarrow-200x=277,6\)
\(\Rightarrow x=-\dfrac{347}{250}\)
Vậy \(x=-\dfrac{347}{250}\)
\(A=\frac{3\left(\frac{1}{2}+\frac{1}{3}-\frac{1}{4}\right)}{5\left(\frac{1}{2}+\frac{1}{3}-\frac{1}{4}\right)}-\frac{3\left(\frac{1}{8}-\frac{1}{10}+\frac{1}{11}+\frac{1}{12}\right)}{5\left(\frac{1}{8}-\frac{1}{10}+\frac{1}{11}+\frac{1}{12}\right)}=\frac{3}{5}-\frac{3}{5}=0\)
Đs:-1,25 nka e
\(-2,5+\left|3x+5\right|=-1,25=>\left|3x+5\right|=-1,25-\left(-2,5\right)=-1,25+2,5=1,25\)
\(=>\orbr{\begin{cases}3x+5=1,25\\3x+5=-1,25\end{cases}=>\orbr{\begin{cases}3x=1,25-5=-3,75=>x=-3,75:3=-1,25\\3x=-1,25-5=-6,25=>x=-6,25:3=-2,08\left(3\right)\end{cases}}}\)