Tìm x
a, (x+5).(x-2) <0 (x thuộc z)
b, 3./x-5/-4=/1-32/ (x thuộc z)
c,8B - 7 = (-7)x biết B=7-72+73-74+ .....+ 7119 -7120 (x thuộc N)
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a) \(\Rightarrow x^2+4x+25-x^2=3\Rightarrow4x=-22\Rightarrow x=-\dfrac{11}{2}\)
b) \(\Rightarrow\left(4x+3-2x+3\right)\left(4x+3+2x-3\right)=0\)
\(\Rightarrow2\left(x+3\right).6x=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=-3\end{matrix}\right.\)
a)
`x/(-8)=5/4`
`=>x*4=5*(-8)`
`=>4x=-40`
`=>x=-40:4`
`=>x=-10`
b)
`(-13)/x=(-65)/10`
`=>(-13)/x=(-13)/2`
`=>x=2`
c)
`(-6)/5=(-12)/x`
`<=>(-12)/10=(-12)/x`
`<=>x=10`
d)
`(x-2)/2=8/(x-2)`
`=>(x-2)(x-2)=8*2`
`=>(x-2)^2=16`
`=>x-2=4` hoặc`x-2=-4`
`=>x=4+2` hoặc `x=-4+2`
`=>x=6` hoặc `x=-2`
`x/(-8) = 5/4`
`=> 4x=5.(-8)`
`=>4x=-40`
`=>x=-40:4`
`=>x=-10`
__
`-13/x =-65/10`
`=> -65x=-130`
`=>x=-130:(-65)`
`=>x= 2`
__
`-6/5 =-12/x`
`=> -6x=-12.5`
`=> -6x= -60`
`=>x=-60:(-6)`
`=>x=10`
__
`(x-2)/2 = 8/(x-2)`
`=>(x-2)^2=2.8`
`=>(x-2)^2=16`
`=> (x-2)^2=+-4^2`
\(\Rightarrow\left[{}\begin{matrix}x-2=4\\x-2=-4\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=6\\x=-2\end{matrix}\right.\)
\(a,x=\dfrac{1}{2}-\dfrac{2}{5}\)
\(x=\dfrac{1}{10}\)
\(b,x+\dfrac{3}{7}=\dfrac{7}{10}\)
\(x=\dfrac{7}{10}-\dfrac{3}{7}\)
\(x=\dfrac{19}{70}\)
\(c,19-x=\dfrac{17}{20}\)
\(x=19-\dfrac{17}{20}\)
\(x=\dfrac{363}{20}\)
a. \(\dfrac{x}{5}=\dfrac{8}{10}\)
\(\Rightarrow10x=8.5\)
\(\Rightarrow10x=40\)
\(\Rightarrow x=\dfrac{40}{10}=4\)
b. \(\dfrac{9}{x}=\dfrac{90}{100}\)
\(\Rightarrow9.100=90x\)
\(\Rightarrow900=90x\)
\(\Rightarrow x=\dfrac{900}{90}=10\)
c. \(17+\dfrac{x}{35}=\dfrac{5}{7}\)
\(\Rightarrow\dfrac{595+x}{35}=\dfrac{25}{35}\)
\(\Rightarrow595+x=25\)
\(\Rightarrow x=25-595=-570\)
d. \(x:\dfrac{5}{27}=\dfrac{2}{9}\)
\(\Rightarrow\dfrac{27x:5}{27}=\dfrac{6}{27}\)
\(\Rightarrow27x:5=6\)
\(\Rightarrow27x=5.6\)
\(\Rightarrow27x=30\)
\(\Rightarrow x=\dfrac{30}{27}=\dfrac{10}{9}\approx1,11\)
a/ x - 7 = 12
=> x = 12 + 7 = 19
b/ 9 + 4(x - 5) = 13
=> 4x - 20 = 4
=> 4x = 24
=> x = 6
c/ (x+2)3 = 64
=> x + 2 = 4
=> x = 2
a) x-7=12
x=12+7
x=19
b) 9+4.(x-5)=13
4.(x-5)=13-9
4.(x-5)=4
(x-5)=4:4
(x-5)=1
x=5+1
x=6
cau cuoi mik ko bt lam nha!
chuc ban hoc tot
a) \(\dfrac{4}{7}\times x=\dfrac{5}{9}+\dfrac{1}{5}=\dfrac{34}{45}\)
\(x=\dfrac{34}{45}:\dfrac{4}{7}=\dfrac{119}{90}\)
b) \(\dfrac{11}{15}:x=\dfrac{2}{3}-\dfrac{9}{15}=\dfrac{1}{15}\)
\(x=\dfrac{11}{15}:\dfrac{1}{15}=11\)
a) 4/7 x X - 1/5 = 5/9
4/7 x X = 5/9 + 1/5
4/7 x X = 34/45
X = 34/45 : 4/7
X = 119/90
b)9/15 + 11/15 : X = 2/3
11/15 : X = 2/3 - 9/15
11/15 : X = 1/15
X = 11/15 : 1/5
X = 11
Tìm x:
\(a.\dfrac{35}{28}-x=\dfrac{5}{14}\\ x=\dfrac{35}{28}-\dfrac{5}{14}\\ x=\dfrac{25}{28}\\ b.\dfrac{6}{7}\times x=\dfrac{2}{3}\\ x=\dfrac{2}{3}:\dfrac{6}{7}\\ x=\dfrac{7}{9}\\ c.x\times7=\dfrac{3}{4}\\ x=\dfrac{3}{4}:7\\ x=\dfrac{3}{28}\\ d.2:x-\dfrac{1}{3}=\dfrac{2}{5}\\ 2:x=\dfrac{2}{5}+\dfrac{1}{3}\\ 2:x=\dfrac{11}{15}\\ x=2:\dfrac{11}{15}\\ x=\dfrac{30}{11}.\)
\(a,\dfrac{35}{28}-x=\dfrac{5}{14}\)
\(x=\dfrac{35}{28}-\dfrac{5}{14}\)
\(x=\dfrac{25}{28}\)
\(b,\dfrac{6}{7}\times x=\dfrac{2}{3}\)
\(x=\dfrac{2}{3}:\dfrac{6}{7}\)
\(x=\dfrac{7}{9}\)
\(c,x\times7=\dfrac{3}{4}\)
\(x=\dfrac{3}{4}:7\)
\(x=\dfrac{3}{28}\)
\(d,2:x-\dfrac{1}{3}=\dfrac{2}{5}\)
\(2:x=\dfrac{2}{5}+\dfrac{1}{3}\)
\(2:x=\dfrac{11}{15}\)
\(x=2:\dfrac{11}{15}\)
\(x=\dfrac{30}{11}\)
#YVA
a: =>x^2-25-x^2-3x=10
=>-3x=35
=>x=-35/3
b: =>4x^2-9-4(x^2+4x+4)=5
=>4x^2-9-4x^2-16x-16-5=0
=>-16x-30=0
=>x=-15/8
c: =>9x^2+45x-9x^2+4=7
=>45x=3
=>x=1/15
d: =>x^3+3x^2+3x+1-x^3-3x^2+5x=8
=>8x=7
=>x=7/8
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