60%.X+2/3=1/3.6+1/3
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a) \(60\%x+\frac{2}{3}x=\frac{1}{3}.6\frac{1}{3}\)
=> \(\frac{3}{5}x+\frac{2}{3}x=\frac{19}{9}\)
=> \(\frac{19}{15}x=\frac{19}{9}\)
=> \(x=\frac{19}{9}:\frac{19}{15}\)
=> \(x=\frac{5}{3}\)
b) (-0,6x - 1/3) . 3/5 - (-1) = 1/3
=> (-3/5x - 1/3) .3/5 = 1/3 - 1
=> (-3/5x - 1/3).3/5 = -2/3
=> -3/5x - 1/3 = -2/3 : 3/5
=> -3/5x - 1/3 = -10/9
=> -3/5x = -10/9 + 1/3
=> -3/5x = -7/9
=> x = -7/9 : (-3/5)
=> x = 35/27
a,60%x+2/3x=1/3.6 1/3
x(60%+2/3)=19/6
x.19/15=19/6
x=19/6 : 19/15
x=5/2
b,[-0,6x-1/2].3/4-(-1)=1/3
(-3/5x-1/2).3/4=1/3-1
(-3/5x-1/2).3/4=-2/3
-0,6x-0,5=-2/3:3/4
................................
c,2[1/2x-1/3]-3/2=1/4
....................................... (tương tự...)
d,Số đó là:720% : 2/3=10,8
Bài 1:
a) Ta có: \(\dfrac{7^4\cdot3-7^3}{7^4\cdot6-7^3\cdot2}\)
\(=\dfrac{7^3\cdot\left(7\cdot3-1\right)}{7^3\cdot2\left(7\cdot3-1\right)}\)
\(=\dfrac{1}{2}\)
c) Ta có: \(E=1+\dfrac{1}{3}+\dfrac{1}{3^2}+...+\dfrac{1}{3^{100}}\)
\(\Leftrightarrow\dfrac{1}{3}\cdot E=\dfrac{1}{3}+\dfrac{1}{3^2}+\dfrac{1}{3^3}+...+\dfrac{1}{3^{101}}\)
\(\Leftrightarrow E-\dfrac{1}{3}\cdot E=1+\dfrac{1}{3}+\dfrac{1}{3^2}+...+\dfrac{1}{3^{100}}-\left(\dfrac{1}{3}+\dfrac{1}{3^2}+\dfrac{1}{3^3}+...+\dfrac{1}{3^{101}}\right)\)
\(\Leftrightarrow E\cdot\dfrac{2}{3}=1-\dfrac{1}{3^{101}}\)
\(\Leftrightarrow E=\dfrac{3-\dfrac{3}{3^{101}}}{2}=\dfrac{1-\dfrac{1}{3^{100}}}{2}\)
\(P=\dfrac{\left(1+2+3+...+100\right)\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{7}-\dfrac{1}{9}\right)\left(63\cdot1,2-21\cdot3,6\right)}{1-2+3-4+5-6+...+99-100}\)
đề là vậy nhé mn
để ý chút thấy liền ah : 63.1,2-21.3,6=63.1,2-21.3.1,2= 63.1,2- 63.1,2=0
=============================
Ta có P = \(\dfrac{\left(1+2+3+...+100\right)\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{7}-\dfrac{1}{9}\right)\left(63.1,2-21.3,6\right)}{1-2+3-4+5-...+99-100}\)= \(\dfrac{\left(1+2+3+...+100\right)\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{7}-\dfrac{1}{9}\right)0}{1-2+3-4+5-...+99-100}\)= \(\dfrac{0}{1-2+3-4+5-6+...+99-100}=0\)
a/ x/27 = -2/3.6
<=>x . 3,6 = -2 . 27
<=>3,6x = -54
<=>x = -54 : 3.6
<=> x = - 15
b/ /x/+1/2 = 3/4
<=>/x/ = 3/4 - 1/2
<=>/x/ =1/4
=> x=1/4 hoặc x= -1/4 (vì giá trị tuyệt đối của mọi số đều nhận giá trị dương)
Câu 1:
a) \(-\dfrac{3}{7}-\left(\dfrac{2}{3}-\dfrac{3}{7}\right)=\dfrac{-3}{7}-\dfrac{2}{3}+\dfrac{3}{7}=\dfrac{-2}{3}\)
Câu 2:
b) \(\dfrac{2}{15}:\left(\dfrac{1}{3}\cdot\dfrac{4}{5}-\dfrac{1}{3}\cdot\dfrac{6}{5}\right)=\dfrac{2}{15}:\left[\dfrac{1}{3}\left(\dfrac{4}{5}-\dfrac{6}{5}\right)\right]=\dfrac{2}{15}:\left(\dfrac{1}{3}\cdot\dfrac{-2}{5}\right)=\dfrac{2}{15}:\dfrac{-2}{15}=\dfrac{2}{-2}=-1\)
Ta có:
\(60\%X+\dfrac{2}{3}=\dfrac{1}{3}.6+\dfrac{1}{3}\\ < =>60\%X=\dfrac{1}{3}.6+\dfrac{1}{3}-\dfrac{2}{3}\\ < =>60\%X=2+\dfrac{1}{3}-\dfrac{2}{3}\\ < =>60\%X=\dfrac{5}{3}\\ =>X=\dfrac{5}{3}:60\%=\dfrac{25}{9}\)
Vậy: X có giá trị bằng 25/9
thank you so much