3x-30%x=-5,4
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3x2-15x-(3x2-x-2)=30
3x2-15x-3x2+x+2=30
-14x+2=30
-14x=28
x=-2
\(a,\Rightarrow4x^2-20x-4x^2+3x+4x-3=5\\ \Rightarrow-13x=8\Rightarrow x=-\dfrac{8}{13}\\ b,\Rightarrow3x^2-10x+8-3x^2+27x=-3\\ \Rightarrow17x=-11\Rightarrow x=-\dfrac{11}{17}\\ c,\Rightarrow\left(x+3\right)\left(2-x\right)=0\Rightarrow\left[{}\begin{matrix}x=-3\\x=2\end{matrix}\right.\\ d,\Rightarrow2x\left(4x^2-25\right)=0\\ \Rightarrow2x\left(2x-5\right)\left(2x+5\right)=0\Rightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{2}{5}\\x=-\dfrac{2}{5}\end{matrix}\right.\\ e,Sửa:\left(4x-3\right)^2-3x\left(3-4x\right)=0\\ \Rightarrow\left(4x-3\right)^2+3x\left(4x-3\right)=0\\ \Rightarrow\left(4x-3\right)\left(7x-3\right)=0\Rightarrow\left[{}\begin{matrix}x=\dfrac{3}{4}\\x=\dfrac{3}{7}\end{matrix}\right.\)
a.
4x(x-5) - (x-1)(4x-3)-5=0
4x^2-20x-4x^2+3x+4x+3=0
(4x^2-4x^2)+(-20x+3x+4x)+3=0
13x+3 = 0
13x=-3
x=-3/13
b,
(3x-4)(x-2)-3x(x-9)+3=0
3x^2-6x-4x+8 - 3x^2+27x+3=0
(3x^2-3x^2)+(-6x-4x+27x)+(8+3)=0
17x+11=0
17x=-11
x=-11/17
c, 2(x+3)-x^2-3x=0
2(x+3) - x(x+3)=0
(x+3)(2-x)=0
TH1: x+3 = 0; x=-3
TH2: 2-x=0;x=2
a: =>5x=25
hay x=5
b: =>6x=21
hay x=7/2
c: =>2x=4
hay x=2
a ) 10 x X - 1 - 3 - 5 - 7 - ... - 19 = 2 + 4 + 6 + ... + 20
10 x X - 1 - 3 - 5 - 7 - ... - 19 = 110
10 x X - ( 1 + 3 + 5 + 7 + ... + 19 ) = 110
10 x X - 100 = 110
10 x X = 110 + 100
10 x X = 210
X = 210 : 10
X = 21
\(\frac{3x}{2}=\frac{49}{30}\)
3x = 49/15
x = 49/45
b) \(\frac{3x}{2}=-\frac{61}{30}\)
3x = -61/15
x = -61/45
\(\frac{3x}{2}=\frac{49}{30}\Rightarrow3x=\frac{49.2}{30}=\frac{49}{15}\Rightarrow x=\frac{49}{45}\)
\(\frac{3x}{2}=\frac{-61}{30}\Rightarrow3x=\frac{\left(-61\right).2}{30}=\frac{-61}{15}\Rightarrow x=\frac{-61}{45}\)
\(3x-30\%x=-5.4\)
\(3x-\frac{3}{10}x=-\frac{27}{5}\)
\(\left(3-\frac{3}{10}\right)x=-\frac{27}{5}\)
\(\frac{27}{10}x=-\frac{27}{5}\)
\(x=-\frac{27}{5}:\frac{27}{10}\)
\(x=-2\)