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3.
a) \(\left|x\right|=2,1\Leftrightarrow\left[\begin{array}{nghiempt}x=2,1\\x=-2,1\end{array}\right.\)
b)\(\left|x\right|=\frac{17}{9}\Leftrightarrow x=-\frac{17}{9}\) (vì x/<0)
c) \(\left|x\right|=1\frac{2}{5}\Leftrightarrow\left|x\right|=\frac{7}{5}\Leftrightarrow\left[\begin{array}{nghiempt}x=\frac{7}{5}\\x=-\frac{7}{5}\end{array}\right.\)
d) \(\left|x\right|=0,35\Leftrightarrow x=0,35\) (Vì x>0)
2.
a) \(\left|x-1,7\right|=2,3\)
\(\Leftrightarrow\begin{cases}x\ge1,7\\x-1,7=2,3\end{cases}\) hoặc \(\begin{cases}x< 1,7\\1,7-x=2,3\end{cases}\)
\(\Leftrightarrow\begin{cases}x\ge1,7\\x=4\left(tm\right)\end{cases}\) hoặc \(\begin{cases}x< 1,7\\x=-0,6\left(tm\right)\end{cases}\)
Vậy x={4;-0,6}
b) đề thiếu
a) |- 2,5| = 2,5 b) |- 2,5| = - 2,5 c) |- 2,5| = - |- 2,5|
>.<
\(\left(-\frac{28}{19}\right)\times\left(-\frac{38}{14}\right)=\frac{14\times2\times19\times2}{19\times14}=4\)
>.<
\(\left(-\frac{21}{16}\right)\times\left(-\frac{24}{7}\right)=\frac{7\times3\times8\times3}{8\times2\times7}=\frac{9}{2}\)
>.<
\(\left(-\frac{12}{17}\right)\times\left(-\frac{34}{9}\right)=\frac{3\times4\times17\times2}{17\times3\times3}=\frac{8}{3}\)
>.<
\(\left|x\right|=2,1\)
\(x=\pm2,1\)
>.<
\(\left|x\right|=\frac{17}{9}\)
\(x=\pm\frac{17}{9}\)
x < 0
\(x=-\frac{17}{9}\)
>.<
\(\left|x\right|=1^2_5\)
\(x=\pm\frac{7}{5}\)
>.<
\(\left|x\right|=0,35\)
\(x=\pm0,35\)
x > 0
x = 0,35
>.<
\(\left|x-1,7\right|=2,3\)
\(x-1,7=\pm2,3\)
Th1:
x - 1,7 = 2,3
x = 2,3 + 1,7
x = 4
Th2:
x - 1,7 = - 2,3
x = - 2,3 + 1,7
x = - 0,6
>.<
\(\left|x+\frac{3}{4}\right|-\frac{1}{3}=0\)
\(\left|x+\frac{3}{4}\right|=\frac{1}{3}\)
\(x+\frac{3}{4}=\pm\frac{1}{3}\)
Th1:
x + 3/4 = 1/3
x = 1/3 - 3/4
x = \(-\frac{5}{12}\)
Th2:
\(x+\frac{3}{4}=-\frac{1}{3}\)
\(x=-\frac{1}{3}-\frac{3}{4}\)
\(x=-\frac{13}{12}\)
A= (3,1 - 2,5) - (-2,5 + 3,1)
=3.1-2.5+2.5-3.1
=0
B= (5,3 - 2,8) - (4 + 5,3)
=5.3 - 2.8-4-5.3
= -6.8
C= -(251.3 + 281) + 3.251 - (1-281)
=-251.3-281+3.251-1+281
=-1
D= -(3/5+3/4)−(−3/4+2/5)
= -3/5-3/4+3/4-2/5
= -5/5
=-1
\(A=\left(3,1-2,5\right)-\left(-2,5+3,1\right)=3,1-2,5+2,5-3,1=0\)
\(B=\left(5,3-2,8\right)-\left(4+5,3\right)=5,3-2,8-4-5,3=-6,8\)
\(C=-\left(215\cdot3+281\right)+3\cdot215-\left(1-281\right)=-215\cdot3-281+3\cdot215-1+281=1\)
\(D=-\left(\frac{3}{5}+\frac{3}{4}\right)-\left(-\frac{3}{4}+\frac{2}{5}\right)=-\frac{3}{5}-\frac{3}{4}+\frac{3}{4}-\frac{2}{5}=-1\)
\(A=\frac{3}{2}+3-2,5+3+1\)
\(A=6\)
\(B=18-\left(-13\right)-16+\left(-27\right)+17-19\)
\(B=18+13-16-27+17-19\)
\(B=-14\)
\(C=[3-\left(A+B\right)-\left(A-B+3\right)]-[\left(A-5\right)-\left(A+5\right)]\)'
\(C=\left(3-A-B-A+B-3\right)-\left(A+5-A-5\right)\)
\(C=-2A-A-5+A+5\)
\(C=-2A\)
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