Đáp án:
a) x+$\frac{1}{5}$ =$\frac{3}{7}$
<=>x=$\frac{3}{7}$-$\frac{1}{5}$
<=>x=$\frac{8}{35}$
vậy x=$\frac{8}{35}$
b)$\frac{11}{12}$-($\frac{2}{5}$+x)=| $\frac{2}{3}$|
<=>-$\frac{2}{5}$-x=$\frac{1}{4}$
<=>x=$\frac{13}{20}$
vậy x=$\frac{13}{20}$
c)2x(x-$\frac{1}{7}$ )=0
<=>\(\left[ \begin{array}{l}x=0\\x=\frac{1}{7}\end{array} \right.\)
vậy x=0;x=$\frac{1}{7}$
d)$\frac{3}{4}$ +$\frac{1}{4}$ :x=$\frac{2}{5}$
<=> 4x=-$\frac{7}{20}$
<=>x=-$\frac{7}{80}$
vậyx=-$\frac{7}{80}$
e)|2.5-x|=1.3
,=>\(\left[ \begin{array}{l}2.5-x=1.3\\2.5-x=-1.3\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=1.2\\x=3.8\end{array} \right.\)
vậy x=1,2,x=3,8
bài2
2$^{x}$ =16
<=>2$^{x}$=2$^{4}$
=>X=4
vậy x=4
b)2$^{3x+2}$ =4$^{x+5}$
=>2$^{3x+2}$ =2$^{2x+10}$
=>3x+2=2x+10
=>3x-2x=10-2
=>x=8
vậy x=8
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