(3x-2)^5=-243
giải ra giúp mình nhé
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1: \(\left(x-3\right)\left(2x-5\right)-3x\left(x+4\right)\)
\(=2x^2-5x-6x+15-3x^2-12x\)
\(=-x^2-23x+15\)
2: \(\left(\dfrac{1}{2}x+5\right)\left(2x-\dfrac{1}{5}\right)\)
\(=x^2-\dfrac{1}{10}x+10x-1\)
\(=x^2+\dfrac{99}{10}x-1\)
\(\frac{3x}{2\cdot5}+\frac{3x}{5\cdot8}+\frac{3x}{8\cdot11}+\frac{3x}{11\cdot14}=\frac{1}{21}\)
\(=>\frac{3x}{3}\left[\frac{3}{2\cdot5}+\frac{3}{5\cdot8}+\frac{3}{8\cdot11}+\frac{3}{11\cdot14}\right]=\frac{1}{21}\)
\(=>x\left[\frac{3}{2\cdot5}+\frac{3}{5\cdot8}+\frac{3}{8\cdot11}+\frac{3}{11\cdot14}\right]=\frac{1}{21}\)
\(=>x\left[\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{11}-\frac{1}{14}\right]=\frac{1}{21}\)
\(=>x\left[\frac{1}{2}-\frac{1}{14}\right]=\frac{1}{21}\)
\(=>x\cdot\frac{3}{7}=\frac{1}{21}\Leftrightarrow x=\frac{1}{9}\)
\(\left(3x-1\right)\left(2x+7\right)-\left(x+1\right)\left(6x-5\right)=16\)
\(\Rightarrow6x^2-19x-7-6x^2-x+5=16\)
\(\Rightarrow-20x=18\Rightarrow x = -\frac{9}{10}\)
xong rùi nha ^^
x + 2x + 3x + ... + 99x = 2 + 4 + 6 + 198 (có 99 số hạng)
x + 2x + 3x + ... + 99x = (198 + 2) . 99 : 2
x .(1 + 2 + 3 + ... + 99) = 9900
x . [(99 + 1) . 99 : 2] = 9900
x . 4950 = 9900
x = 9900 : 4950
x = 2
x+2x+3x+....+99x=2+4+6+..+198
x(1+2+3+4+...+99)=9900
x=9900/4950
x=2
\(\frac{2}{5}+\frac{3}{5}.\left(3x-3\right)=\frac{-5}{10}\)
\(\frac{2}{5}+\frac{3}{5}.3.\left(x-1\right)=\frac{-1}{2}\)
\(\frac{9}{5}.\left(x-1\right)=\frac{-1}{2}-\frac{2}{5}\)
\(\frac{9}{5}.\left(x-1\right)=\frac{-9}{10}\)
\(x-1=\frac{-9}{10}:\frac{9}{5}\)
\(x-1=\frac{-1}{2}\)
\(x=\frac{-1}{2}+1\)
\(x=\frac{1}{2}\)
\(\frac{2}{5}+\frac{3}{5}.\left(3x-3\right)=-\frac{5}{10}\)
\(\frac{3}{5}\left(3x-3\right)=-\frac{5}{10}-\frac{2}{5}\)
\(\frac{3}{5}\left(3x-3\right)=-\frac{9}{10}\)
\(\left(3x-3\right)=-\frac{9}{10}:\frac{3}{5}\)
\(3\left(x-1\right)=-\frac{3}{2}\)
\(x-1=-\frac{1}{2}\)
\(x=\frac{1}{2}\)
Vậy...
1) \(\frac{2}{3}x+\frac{3}{4}\left(x-5\right)=-\frac{5}{6}\)
\(\frac{2}{3}x+\frac{3}{4}x-\frac{15}{4}=-\frac{5}{6}\)
\(\frac{17}{12}x=-\frac{5}{6}+-\frac{15}{4}=-\frac{55}{12}\)
\(x=-\frac{55}{12}:\frac{17}{12}=-\frac{55}{17}\)
0,5x - 2/3x = 5/12
=> x(0,5 - 2/3) = 5/12
=> -1/6x = 5/12
=> x = (5/12) / (-1/6)
=> x = -5/2
2.(5+3x)+x=31
=> 10+6x+x=31
=>10+7x=31
=>7x=31-10=21
=>x=3
#HọcTốt
Nếu x,y thuộc Z
suy ra phương trình tương đương với y(4-x)-3(4-x)=15-12
suy ra (4-x)(y-3)=3
Xét các trường hợp
4-x=1 thì y-3=3
4-x=-1 thì y-3= -3
4-x =3 thì y-3=1
4-x= -3 thì y-3= -1
giải các trường hợp ra tìm x và y
( 3x - 2 ) ^ 5 = ( -3 )^ 5
<=> 3x - 2 = -3
<=> 3x = -3 + 2
<=> 3x = -1
<=> x = -1 / 3
x=1/3