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26 tháng 2 2020
\(1) 2x+1=15-5x \)
\(⇔2x+5x=15-1\)
\(⇔7x=14\)
\(⇔x=2\)
vậy pt có 1 nghiệm là x=2
\(2) 3x-2=2x+5\)
\(⇔3x-2x=5+2\)
\(⇔x=7\)
vậy pt có 1 nghiệm là x=7
\(3) 7(x-2)=5(3x+1)\)
\(⇔7x-14=15x+5\)
\(⇔7x-15x=5+14\)
\(⇔-8x=19\)
\(⇔x=-\dfrac{19}{8}\)
vậy pt có 1 nghiệm là x=-\(\dfrac{19}{8}\)
\(4) 2x+5=20-3x\)
\(⇔2x+3x=20-5\)
\(⇔5x=15\)
\(⇔x=3\)
vậy pt có 1 nghiệm là x=3
\(5) -4x+8=0\)
\(⇔-4x=-8\)
\(⇔x=2\)
vậy pt có 1 nghiệm là x=2
\(6) x-3=10-5x\)
\(⇔x+5x=10+3\)
\(⇔6x=13\)
\(⇔x=\dfrac{13}{6}\)
vậy pt có 1 nghiệm là \(x=\dfrac{13}{6}\)
\(7) 3x-1=x+3\)
\(⇔3x-x=3+1\)
\(⇔2x=4\)
\(⇔x=2\)
vậy pt có 1 nghiệm là x=2
\(8) 2(x+1)=5x-7\)
\(⇔2x+2=5x-7\)
\(⇔2x-5x=-7-2\)
\(⇔-3x=-9\)
\(⇔x=3\)
vậy pt có 1 nghiệm là x=3.
HN
16 tháng 12 2018
\(a,\frac{2x+4}{10}+\frac{2-x}{15}=\frac{\left(2x+4\right).3}{10.3}+\frac{\left(2-x\right).2}{15.2}\)
\(=\frac{6x+12}{30}+\frac{4-2x}{30}=\frac{6x+12+4-2x}{30}=\frac{4x+16}{30}\)
\(=\frac{4.\left(x+4\right)}{30}=\frac{2\left(x+4\right)}{15}\)
\(b,\frac{3x}{10}+\frac{2x-1}{15}+\frac{2-x}{20}=\frac{3x.6}{10.6}+\frac{\left(2x-1\right).4}{15.4}+\frac{\left(2-x\right).3}{20.3}\)
\(=\frac{18x}{60}+\frac{8x-4}{60}+\frac{6-3x}{60}=\frac{18x+8x-4+6-3x}{60}=\frac{23x+2}{60}\)
\(c,\frac{x+1}{2x-2}+\frac{x^2+3}{2-2x^2}=\frac{x+1}{2\left(x-1\right)}+\frac{x^2+3}{2\left(1-x^2\right)}=\frac{x+1}{2\left(x-1\right)}+\frac{-x^2-3}{2\left(x^2-1\right)}\)
\(=\frac{x+1}{2\left(x-1\right)}+\frac{-x^2-3}{2\left(x-1\right)\left(x+1\right)}\)\(=\frac{\left(x+1\right)\left(x+1\right)}{2\left(x-1\right)\left(x+1\right)}+\frac{-x^2-3}{2\left(x-1\right)\left(x+1\right)}\)
\(=\frac{x^2+2x+1-x^2-3}{2\left(x-1\right)\left(x+1\right)}=\frac{2x-2}{2\left(x-1\right)\left(x+1\right)}=\frac{2\left(x-1\right)}{2\left(x-1\right)\left(x+1\right)}\)\(=\frac{1}{x+1}\)
ND
6 tháng 3 2018
1. 3y = 0
=> y = 0
2. 1+x = 0
<+ x = -1
3.
\(1-2t=0\)
\(\Leftrightarrow2t=1\)
\(\Leftrightarrow\dfrac{1}{2}\)
4. 2x +x + 3 =0
\(\Leftrightarrow3x+3=0\)
\(\Leftrightarrow x=-3\)
5.
\(25x-20=0\)
\(\Leftrightarrow25x=20\)
\(\Leftrightarrow x=\dfrac{4}{5}\)
ND
6 tháng 3 2018
7.
2x-3 = x+5
<=> 2x - x = 5+3
<=> x = 8
8.
x-8=2x+3
<=> x - 2x = 3+8
<=> -x = 11
<=> x = -11
9. 17-2x = 3x-5
<=> -2x-3x = -5-17
<=> -5x = -22
<=> x = \(\dfrac{22}{5}\)
10.
2x+x+22=0
<=> 3x+22=0
<=> 3x = -22
<=> x = \(\dfrac{-22}{3}\)
Mấy bài kia tự giải tương tự nhá!!!
26 tháng 3 2020
1) Ta có: \(5\left(x-2\right)=3x+10\)
\(\Leftrightarrow5x-10-3x-10=0\)
\(\Leftrightarrow2x-20=0\)
\(\Leftrightarrow2\left(x-10\right)=0\)
Vì 2>0
nên x-10=0
hay x=10
Vậy: x=10
2) Ta có: \(x^2\left(x-5\right)-4x+20=0\)
\(\Leftrightarrow x^2\left(x-5\right)-4\left(x-5\right)=0\)
\(\Leftrightarrow\left(x-5\right)\left(x^2-4\right)=0\)
\(\Leftrightarrow\left(x-5\right)\left(x-2\right)\left(x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-5=0\\x-2=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=2\\x=-2\end{matrix}\right.\)
Vậy: x∈{-2;2;5}
3) Ta có: \(\frac{3x+1}{4}+\frac{8x-21}{20}=\frac{3\left(x+2\right)}{5}-2\)
\(\Leftrightarrow\frac{5\left(3x+1\right)}{20}+\frac{8x-21}{20}-\frac{12\left(x+2\right)}{20}+\frac{40}{20}=0\)
\(\Leftrightarrow15x+5+8x-21-12\left(x+2\right)+40=0\)
\(\Leftrightarrow15x+5-8x-21-12x-24+40=0\)
\(\Leftrightarrow-5x=0\)
hay x=0
Vậy: x=0
4) ĐKXĐ: x≠5; x≠-5
Ta có: \(\frac{3}{4x-20}+\frac{7}{6x+30}=\frac{15}{2x^2-50}\)
\(\Leftrightarrow\frac{3}{4\left(x-5\right)}+\frac{7}{6\left(x+5\right)}-\frac{15}{2\left(x-5\right)\left(x+5\right)}=0\)
\(\Leftrightarrow\frac{9\left(x+5\right)}{12\left(x-5\right)\left(x+5\right)}+\frac{14\left(x-5\right)}{12\left(x+5\right)\left(x-5\right)}-\frac{180}{12\left(x-5\right)\left(x+5\right)}=0\)
\(\Leftrightarrow9x+45+14x-70-180=0\)
\(\Leftrightarrow23x-205=0\)
\(\Leftrightarrow23x=205\)
hay \(x=\frac{205}{23}\)(tm)
Vậy: \(x=\frac{205}{23}\)
21 tháng 10 2022
a: \(=\dfrac{6x+12+4-2x}{30}=\dfrac{4x+16}{30}=\dfrac{2x+8}{15}\)
b: \(=\dfrac{18x}{60}+\dfrac{8x-4}{60}+\dfrac{6-3x}{60}\)
\(=\dfrac{18x+8x-4+6-3x}{60}=\dfrac{23x+2}{60}\)
c: \(=\dfrac{x+1}{2\left(x-1\right)}-\dfrac{x^2+3}{2\left(x-1\right)\left(x+1\right)}\)
\(=\dfrac{x^2+2x+1-x^2-3}{2\left(x-1\right)\left(x+1\right)}=\dfrac{2x-2}{2\left(x-1\right)\left(x+1\right)}=\dfrac{1}{x+1}\)
d: \(=\dfrac{x}{y\left(x-y\right)}+\dfrac{2x-y}{x\left(y-x\right)}\)
\(=\dfrac{x^2-2xy+y^2}{xy\left(x-y\right)}=\dfrac{x-y}{xy}\)
e: \(=\dfrac{x^2+2xy+y^2+x^2+y^2}{x+y}=\dfrac{2x^2+2xy+2y^2}{x+y}\)
22 tháng 5 2022
a: \(\left(2x-3\right)\left(3x^2+1\right)-6x\left(x^2-x+1\right)+3x^2-2x=10\)
\(\Leftrightarrow6x^3+2x-9x^2-3-6x^3+6x^2-6x+3x^2-2x=10\)
\(\Leftrightarrow-6x-3=10\)
=>-6x=13
hay x=-13/6
b: \(\Leftrightarrow3x^2-3x+x-2-3x^2+5x=-8-5x\)
=>3x-2=-5x-8
=>8x=-6
hay x=-3/4
c: \(\Leftrightarrow64x^3-27-64x^3+32x^2-32x^2+x=20\)
=>x-27=20
hay x=47
31 tháng 3 2019
a,\(2\left(2x-3\right)\ge5\left(2+x\right)+13\)
\(\Leftrightarrow4x-6\ge10+5x+13\)
\(\Leftrightarrow4x-5x\ge10+13+6\)
\(\Leftrightarrow-x\ge29\)
\(\Leftrightarrow x\ge-29\)