[ 3,8 : ( X + 1.05 ) ] : 1/3 = 2 \(\frac{1}{9}\)
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( x - 1,3 ) + ( x + 2,5 ) + ( x - 3,8 ) = 1,9
x - 1,3 + x + 2,5 + x - 3,8 = 1,9
3x - 2,6 = 1,9
3x = 4,5
\(\frac{x}{3}+\frac{x}{6}+\frac{x}{9}=2\frac{1}{3}\)
\(\frac{6x}{18}+\frac{3x}{18}+\frac{2x}{18}=\frac{7}{3}\)
\(\frac{11x}{18}=\frac{42}{18}\)
\(\Rightarrow11x=42\)
\(\Rightarrow x=\frac{42}{11}\)
\(\left(\frac{5}{7}+\frac{2}{3}\right).\frac{7}{11}\)
C1:\(=\frac{29}{21}.\frac{7}{11}=\frac{29}{33}\)(tính trong ngoặc rồi mới nhân)
C2:\(=\frac{5}{7}.\frac{7}{11}+\frac{2}{3}.\frac{7}{11}=\frac{5}{11}+\frac{14}{33}=\frac{29}{33}\)(dùng tính chất phân phối)
Những câu khác bn tự làm nha
a)
\((3x-7)^5=0\Rightarrow 3x-7=0\Rightarrow x=\frac{7}{3}\)
b)
\(\frac{1}{4}-(2x-1)^2=0\)
\(\Leftrightarrow (2x-1)^2=\frac{1}{4}=(\frac{1}{2})^2=(-\frac{1}{2})^2\)
\(\Rightarrow \left[\begin{matrix} 2x-1=\frac{1}{2}\\ 2x-1=\frac{-1}{2}\end{matrix}\right.\Rightarrow \Rightarrow \left[\begin{matrix} x=\frac{3}{4}\\ x=\frac{1}{4}\end{matrix}\right.\)
c)
\(\frac{1}{16}-(5-x)^3=\frac{31}{64}\)
\(\Leftrightarrow (5-x)^3=\frac{1}{16}-\frac{31}{64}=\frac{-27}{64}=(\frac{-3}{4})^3\)
\(\Leftrightarrow 5-x=\frac{-3}{4}\)
\(\Leftrightarrow x=\frac{23}{4}\)
d)
\(2x=(3,8)^3:(-3,8)^2=(3,8)^3:(3,8)^2=3,8\)
\(\Rightarrow x=3,8:2=1,9\)
e)
\((\frac{27}{64})^9.x=(\frac{-3}{4})^{32}\)
\(\Leftrightarrow [(\frac{3}{4})^3]^9.x=(\frac{3}{4})^{32}\)
\(\Leftrightarrow (\frac{3}{4})^{27}.x=(\frac{3}{4})^{32}\)
\(\Leftrightarrow x=(\frac{3}{4})^{32}:(\frac{3}{4})^{27}=(\frac{3}{4})^5\)
f)
\(5^{(x+5)(x^2-4)}=1\)
\(\Leftrightarrow (x+5)(x^2-4)=0\)
\(\Leftrightarrow \left[\begin{matrix} x+5=0\\ x^2-4=0\end{matrix}\right.\Leftrightarrow \left[\begin{matrix} x+5=0\\ x^2=4=2^2=(-2)^2\end{matrix}\right.\)
\(\Rightarrow \left[\begin{matrix} x=-5\\ x=\pm 2\end{matrix}\right.\)
g)
\((x-2,5)^2=\frac{4}{9}=(\frac{2}{3})^2=(\frac{-2}{3})^2\)
\(\Rightarrow \left[\begin{matrix} x-2,5=\frac{2}{3}\\ x-2,5=\frac{-2}{3}\end{matrix}\right.\Rightarrow \left[\begin{matrix} x=\frac{19}{6}\\ x=\frac{11}{6}\end{matrix}\right.\)
h)
\((2x+\frac{1}{3})^3=\frac{8}{27}=(\frac{2}{3})^3\)
\(\Rightarrow 2x+\frac{1}{3}=\frac{2}{3}\Rightarrow x=\frac{1}{6}\)
Trả lời :
a, x = (3,8)3 - (- 3,8)2
=> x = (3,8)3 - (3,8)2
=> x = (3,8)3 - 2
=> x = 3,8
Bài làm:
a) \(x=\left(3,8\right)^3\div\left(-3,8\right)^2\)
\(\Leftrightarrow x=\left(3,8\right)^3\div\left(3,8\right)^2\)
\(\Rightarrow x=3,8\)
b) đề sai sai ý bn
[ 3,8 : ( x + 1,05 ) ] : 1/3 = 2 1/9
19/5 : ( x + 1,05 ) = 21/9 x 1/3
19/5 : ( x + 1,05) = 7/9
x + 1,05 = 19/5 : 7/9
x + 21/20 = 171/35
x = 171/35 - 21/20
x = 228/49
[ 3,8 : ( x + 1,05 ) ] : 1/3 = 2 1/9
=> 3,8 : ( x+1,05) = 19/9 x 1/ 3 = 19/27
=> x + 1,05 = 3,8 : 19/27 = 5,4
=> x= 5,4-1,05 = 4,35
\(9^{x-1}=\frac{1}{9}\Rightarrow9^{x-1}=9^{-1}\Rightarrow x-1=-1\Rightarrow x=0\)
\(x-3,8=-15,3-1,3x\)
\(\Rightarrow x+1,3x=-15,3+3,8\)
\(\Rightarrow2,3x=-11,5\)
\(\Rightarrow x=-11,5:2,3=-5\)
\(\frac{x+2}{7}=\frac{y-3}{5}=\frac{z}{3}=\frac{x+2+y-3-z}{7+5-3}=\frac{x+y-z-1}{9}=\frac{-17-1}{9}=-\frac{18}{9}=-2\)(t/c dãy tỉ số = nhau)
\(\Rightarrow\frac{x+2}{7}=-2\Rightarrow x+2=-2.7=-14\Rightarrow x=-14-2=-16\)
\(\Rightarrow\frac{y-3}{5}=-2\Rightarrow y-3=-2.5=-10\Rightarrow y=-10+3=-7\)
\(\Rightarrow\frac{z}{3}=-2\Rightarrow z=-2.3=-6\)
\(\Leftrightarrow\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{19}-\frac{1}{21}\right).462-\frac{17}{x+1,05}=19.\)
\(\Leftrightarrow\left(\frac{1}{11}-\frac{1}{21}\right)462-\frac{17}{x+1,05}=19\)
\(\Leftrightarrow20-\frac{17}{x+1,05}=19\)
\(\Leftrightarrow1-\frac{17}{x+1,05}=0\)
\(\Leftrightarrow x+1,05=17\)
\(\Leftrightarrow x=15,95\)