x+1/5x-1/3x=-26/5
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a) \(\Rightarrow x\left(x+3\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=-3\end{matrix}\right.\)
b) \(\Rightarrow x\left(x^2-4\right)=0\Rightarrow x\left(x-2\right)\left(x+2\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=2\\x=-2\end{matrix}\right.\)
c) \(\Rightarrow\left(x-1\right)\left(5x-1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=1\\x=\dfrac{1}{5}\end{matrix}\right.\)
d) \(\Rightarrow2\left(x+5\right)-x\left(x+5\right)=0\Rightarrow\left(x+5\right)\left(2-x\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=-5\\x=2\end{matrix}\right.\)
e) \(\Rightarrow2x^2-10x-3x-2x^2=26\)
\(\Rightarrow-13x=26\Rightarrow x=-2\)
f) \(\Rightarrow\left(x-2012\right)\left(5x-1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=2012\\x=\dfrac{1}{5}\end{matrix}\right.\)
1) (2x + 1)(3x – 2) = (5x – 8)(2x + 1)
⇔ (2x + 1)(3x – 2) – (5x – 8)(2x + 1) = 0
⇔ (2x + 1).[(3x – 2) – (5x – 8)] = 0
⇔ (2x + 1).(3x – 2 – 5x + 8) = 0
⇔ (2x + 1)(6 – 2x) = 0
⇔\(\left[{}\begin{matrix}2x+1=0\\6-2x=0\end{matrix}\right.\) ⇔ \(\left[{}\begin{matrix}x=\dfrac{-1}{2}\\x=3\end{matrix}\right.\)
Vậy.....
2) 4x2 -1 = (2x + 1)(3x - 5)
⇔ (2x-1)(2x+1)-(2x+1)(3x-5)=0
⇔ (2x+1)(2x-1-3x+5)=0
⇔ (2x+1)(4-x)=0
⇔ \(\left[{}\begin{matrix}2x+1=0\\4-x=0\end{matrix}\right.\) ⇔ \(\left[{}\begin{matrix}x=\dfrac{-1}{2}\\x=4\end{matrix}\right.\)
Vậy...
3)
(x + 1)2 = 4(x2 – 2x + 1)
⇔ (x + 1)2 - 4(x2 – 2x + 1) = 0
⇔ x2 + 2x +1- 4x2 + 8x – 4 = 0
⇔ - 3x2 + 10x – 3 = 0
⇔ (- 3x2 + 9x) + (x – 3) = 0
⇔ -3x (x – 3)+ ( x- 3) = 0
⇔ ( x- 3) ( - 3x + 1) = 0
⇔\(\left[{}\begin{matrix}x-3=0\\-3x+1=0\end{matrix}\right.\) ⇔\(\left[{}\begin{matrix}x=3\\x=\dfrac{1}{3}\end{matrix}\right.\)
Vậy......
a)\(5\left(2x-1\right)-4\left(8-3x\right)=7\)
\(\Leftrightarrow10x-5+12x-32=7\)
\(\Leftrightarrow22x-37=7\)
\(\Leftrightarrow22x=44\Rightarrow x=2\)
b)\(5x\left(x-5\right)-x\left(2x+3\right)=26\)
\(\Leftrightarrow5x^2-25x-2x^2-3x=26\)
\(\Leftrightarrow3x^2-28x-26=0\)
\(\Leftrightarrow3\left(x-\dfrac{14}{3}\right)^2-\dfrac{274}{3}=0\)
\(\Rightarrow x=\dfrac{14}{3}\pm\dfrac{\sqrt{274}}{3}\)
1) \(6x+3=0\Leftrightarrow6x=-3\Leftrightarrow x=-\dfrac{1}{2}\)
2) \(-5x-7=0\Leftrightarrow-5x=7\Leftrightarrow x=-\dfrac{7}{5}\)
3) \(\left(3x-2\right)\left(5-x\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}3x-2=0\\5-x=0\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=5\end{matrix}\right.\)
4) \(x^2-3x=0\Leftrightarrow x\left(x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)
6) \(x^4+8=0\)( vô lý do \(x^4+8\ge8>0\))
Vậy \(S=\varnothing\)
\(x-\frac{1}{3}x+\frac{1}{5}x=\frac{-26}{x}\)
\(x-\frac{5}{15}x+\frac{3}{15}x=\frac{-26}{x}\)
\(x.\left(1-\frac{5}{15}+\frac{3}{15}\right)=\frac{-26}{x}\)
\(x.\left(\frac{15}{15}-\frac{5}{15}+\frac{3}{15}\right)=\frac{-26}{x}\)
\(x.\frac{13}{15}=\frac{-26}{x}\)
\(\frac{13x}{15}=\frac{-26}{x}\)
\(13x.x=-26.15\)
\(13x^2=-390\)
\(x^2=-390:13\)
\(x^2=-30\)
\(1,x^3-3x^2=0\)
\(x^2\left(x-3\right)=0\)
\(\orbr{\begin{cases}x^2=0\\x-3=0\end{cases}\orbr{\begin{cases}x=0\left(TM\right)\\x=3\left(TM\right)\end{cases}}}\)
\(2,3x^3-48x=0\)
\(3x\left(x^2-16\right)=0\)
\(\orbr{\begin{cases}3x=0\\x^2-16=0\end{cases}\orbr{\begin{cases}x=0\left(TM\right)\\x^2=16\end{cases}\orbr{\begin{cases}x=0\left(TM\right)\\x=\pm4\left(TM\right)\end{cases}}}}\)
\(3,5x\left(x-1\right)=x-1\)
\(5x^2-5x=x-1\)
\(5x^2-6x+1=0\)
\(5x^2-5x-x+1=0\)
\(5x\left(x-1\right)-\left(x-1\right)=0\)
\(\left(5x-1\right)\left(x-1\right)=0\)
\(\orbr{\begin{cases}5x-1=0\\x-1=0\end{cases}\orbr{\begin{cases}x=\frac{1}{5}\left(TM\right)\\x=1\left(TM\right)\end{cases}}}\)
\(4,2\left(x+5\right)-x^2-5x=0\)
\(2x+10-x^2-5x=0\)
\(-x^2-3x+10=0\)
\(-x^2-5x+2x+10=0\)
\(-x\left(x+5\right)+2\left(x+5\right)=0\)
\(\left(x+5\right)\left(2-x\right)=0\)
\(\orbr{\begin{cases}x+5=0\\2-x=0\end{cases}\orbr{\begin{cases}x=-5\left(TM\right)\\x=2\left(TM\right)\end{cases}}}\)
\(5,2x\left(x-5\right)-x\left(3+2x\right)=26\)
\(2x^2-10x-3x-2x^2=26\)
\(-13x-26=0\)
\(-13\left(x+2\right)=0\)
\(x=-2\left(TM\right)\)
Trả lời:
1, \(x^3-3x^2=0\)
\(\Leftrightarrow x^2\left(x-3\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x^2=0\\x-3=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0\\x=3\end{cases}}}\)
Vậy x = 0; x = 3 là nghiệm của pt.
2, \(3x^3-48x=0\)
\(\Leftrightarrow3x\left(x^2-16\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}3x=0\\x^2-16=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0\\x=\pm4\end{cases}}}\)
Vậy x = 0; x = 4; x = - 4 là nghiệm của pt.
3, \(5x\left(x-1\right)=x-1\)
\(\Leftrightarrow5x\left(x-1\right)-\left(x-1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(5x-1\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-1=0\\5x-1=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=1\\x=\frac{1}{5}\end{cases}}}\)
Vậy x = 1; x = 1/5 là nghiệm của pt.
4, \(2\left(x+5\right)-x^2-5x=0\)
\(\Leftrightarrow2\left(x+5\right)-x\left(x+5\right)=0\)
\(\Leftrightarrow\left(x+5\right)\left(2-x\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x+5=0\\2-x=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-5\\x=2\end{cases}}}\)
Vậy x = - 5; x = 2 là nghiệm của pt.
5, \(2x\left(x-5\right)-x\left(3+2x\right)=26\)
\(\Leftrightarrow2x^2-10x-3x-2x^2=26\)
\(\Leftrightarrow-13x=26\)
\(\Leftrightarrow x=-2\)
Vậy x = - 2 là nghiệm của pt.
\(\frac{x+1}{5x}-\frac{1}{3x}=\frac{-26}{5}\)
\(\Leftrightarrow\frac{\left(x-1\right)3-5}{15x}=\frac{-26}{5}\)
\(\Leftrightarrow\frac{3x+3-5}{15x}+\frac{26}{5}=0\Leftrightarrow\frac{3x-2+26.3x}{15x}=0\)
\(\Leftrightarrow\)\(\frac{81x-2}{15x}=0\)
\(\Rightarrow81x-2=0\Rightarrow x=\frac{2}{81}\)
x + 1/5x - 1/3x = -26/5
x(1 + 1/5 - 1/3) = -26/5
13/15x = -26/5
x = -26/5 : 13/15
x = -6