x+100=1300
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29 tháng 9 2018
ta có: \(\frac{x}{\frac{y}{z}}=\frac{3}{\frac{4}{5}}\Rightarrow\frac{x}{3}=\frac{y}{4}=\frac{z}{5}\Rightarrow\frac{x^2}{9}=\frac{y^2}{16}=\frac{z^2}{25}=\frac{2x^2}{18}=\frac{2y^2}{32}=\frac{3z^2}{75}.\)
ADTCDTSBN
...
bn tu lm tiep nha
3 tháng 9 2023
a) \(\left(\dfrac{1}{2}+\dfrac{1}{6}+...+\dfrac{1}{90}\right)\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=89\)
\(\Rightarrow\left(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+...+\dfrac{1}{9\cdot10}\right)\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)\right]:\dfrac{1}{2}=89\)
\(\Rightarrow\left(1-\dfrac{1}{2}+\dfrac{1}{2}-...+\dfrac{1}{9}-\dfrac{1}{10}\right)\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)\right]:\dfrac{1}{2}=89\)
\(\Rightarrow\left(1-\dfrac{1}{10}\right)\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)\right]:\dfrac{1}{2}=89\)
\(\Rightarrow\dfrac{9}{10}\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)\right]:\dfrac{1}{2}=89\)
\(\Rightarrow90-\left[\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)\right]:\dfrac{1}{2}=89\)
\(\Rightarrow\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)=90-89\)
\(\Rightarrow\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)=1\)
\(\Rightarrow x+\dfrac{103}{50}=\dfrac{5}{2}\)
\(\Rightarrow x=\dfrac{11}{25}\)
b) \(x\cdot9,85+x\cdot0,15=0,1\)
\(\Rightarrow x\cdot\left(9,85+0,15\right)=0,1\)
\(\Rightarrow x\cdot10=0,1\)
\(\Rightarrow x=\dfrac{0,1}{10}\)
\(\Rightarrow x=0,01\)
c) \(\dfrac{2}{5}+2022x=\dfrac{4}{10}\)
\(\Rightarrow\dfrac{2}{5}+2022x=\dfrac{2}{5}\)
\(\Rightarrow2022x=\dfrac{2}{5}-\dfrac{2}{5}\)
\(\Rightarrow2022x=0\)
\(\Rightarrow x=\dfrac{0}{2022}\)
\(\Rightarrow x=0\)
3 tháng 9 2023
a) \(\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+...+\dfrac{1}{90}\right).100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=89\left(1\right)\)
Ta có :
\(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+...+\dfrac{1}{90}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{9}-\dfrac{1}{10}\)
\(=1-\dfrac{1}{10}=\dfrac{9}{10}\)
\(\left(1\right)\Rightarrow\dfrac{9}{10}.100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=89\)
\(\Rightarrow90-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right].2=89\)
\(\Rightarrow\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right].2=90-89\)
\(\Rightarrow\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)=\dfrac{1}{2}\)
\(\Rightarrow x+\dfrac{206}{100}=\dfrac{5}{2}:\dfrac{1}{2}\)
\(\Rightarrow x+\dfrac{103}{50}=\dfrac{5}{2}.\dfrac{2}{1}\)
\(\Rightarrow x+\dfrac{103}{50}=5\)
\(\Rightarrow x=5-\dfrac{103}{50}\)
\(\Rightarrow x=\dfrac{250}{50}-\dfrac{103}{50}\)
\(\Rightarrow x=\dfrac{147}{50}\)
15 tháng 10 2016
C=(1x3+3x5+...+99x101)+(2x4+4x6+...+98x100)
đặt S=1x3+3x5+...+99x101
=>6S=6x(1x3+3x5+...+99x101)
=1x3x(5+1)+3x5x(7-1)+...+97x99x(101-95)+99x101x(103-97)
=1x3x5+1x3x1+3x5x7-1x3x5+....+97x99x101-95x97x99+99x101x103-97x99x101
=1x3x1+99x101x103
=>S=(3+99x101x103):6=171650
=>C=171650+(2x4+4x6+...+98x100)
đặt A=2x4+4x6+...+98x100
=>6A=6x(2x4+4x6+...+98x100)
=>6A=2x4x6+4x6x(8-2)+...+96x98x(100-94)+98x100x(102-96)
=2x4x6+4x6x8-2x4x6+...+96x98x100-94x96x98+98x100x102-96x98x100
=98x100x102
=>A=98x100x102:6=166600
=>C=166600+171650
=>C=338250
B=2x2+4x4+6x6+...+100x100
=2x(4-2)+4x(6-2)+6x(8-2)+...+100x(102-2)
=2x4-4+4x6-8+6x8-12+...+100x102-200
=(2x4+4x6+6x8+...+100x102)-(4+8+12+...+200)
đặt A=2x4+4x6+...+98x100+100x102
=>6A=6x(2x4+4x6+...+98x100+100x102)
=>6A=2x4x6+4x6x(8-2)+...+96x98x(100-94)+98x100x(102-96)+100x102x(104-98)
=2x4x6+4x6x8-2x4x6+...+96x98x100-94x96x98+98x100x102-96x98x100+100x102x104-98x100x102
=100x102x104
=>A=100x102x104:6=176800
=>B=176800-(4+8+12+...+200)
đặt S=4+8+12+..+200
Số số hạng của S là:
(200-4):4+1=50 số
S=(200+4)x50:2=5100
=>B=176800-5100
=>B=171700
LM
12 tháng 8 2016
= 111...1 x (100...0 - 1)
100 cs 1 100 cs 0
= 111...1 000...0 - 111...1
100 cs 1 100cs 0 100 cs 1
= 111...10888...89
99 cs 1 99 cs 8
17 tháng 7 2017
a) -12( x - 5 ) + 7( 3 - x ) = 5
-12x + 60 + 21 - 7x = 5
-19x = 5 -81
-19x = -76
x = 76:19
x= 4
17 tháng 7 2017
b) 30.( x + 2 ) - 6( x - 5 ) - 24x = 100
30x + 60 - 6x + 30 - 24x = 100
0x = 100 - 60 - 30
0x = 10
=> ko có giá trị x thỏa mãn đề bài
x=1200
bạn nhé
tk nha@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
thanks
x=1200
bạn nhé
tk nha@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
thanks