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a) \(5x\left(x-7\right)-30\cdot\left(x-7\right)=0\)
\(\Rightarrow\left(5x-30\right)\left(x-7\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}5x-30=0\\x-7=0\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=6\\x=7\end{matrix}\right.\)
b) \(\left(2x-4\right)\left(2x+4\right)-x\left(x+3\right)=3x\left(x+5\right)\)
\(\Rightarrow4x^2-16-x^2-3x=3x^2+15x\)
\(\Rightarrow-16=18x\Rightarrow x=-\dfrac{8}{9}\)
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\(a,\) \(5x\left(4-x\right)+\left(5x^2-12\right)=x+6\)
\(< =>20x-5x^2+5x^2-12-x-6=0\)
\(< =>19x-18=0\)
\(< =>x=\dfrac{18}{19}\)
\(b,\left(2x-7\right)\left(5+4x\right)-8\left(x^2-4x+5\right)=-30\)
\(< =>10x+8x^2-35-28x-8x^2+24x-40+30=0\)
\(< =>6x-45=0< =>x=\dfrac{45}{6}=7,5\)
a) \(5x\left(4-x\right)+\left(5x^2-12\right)=x+\Rightarrow6\\ \Leftrightarrow20x-5x^2+5x^2-12=x+6\\ \Leftrightarrow20x-12=x+6\\\Rightarrow20x-x=6+12\\ \Rightarrow19x=18\\ \Rightarrow x=\dfrac{18}{19}\)
b) \(\left(2x-7\right)\left(5+4x\right)-8\left(x^2-3x+5\right)=-30\\ \Rightarrow10x+8x^2-35-28x-8x^2+24x-40=-30\\ \Rightarrow6x-75=-30\\ \Rightarrow6x=45\\ \Rightarrow x=\dfrac{15}{2}\)
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a) 36x2 -12x - 36x2 +27x = 30
<=> 15x = 30
<=> x = 2
Chúc bạn làm bài tốt
a) \(3x.\left(12x-4\right)-9x.\left(4x-3\right)=30\)
<=> \(36x^2-12x-36x^2+27x=30\)
<=> 15x=30 <=> x=2
![](https://rs.olm.vn/images/avt/0.png?1311)
a, \(x\left(x-4\right)=x\left(x+5\right)-12\)
\(\Rightarrow x^2-4x=x^2+5x-12\)
\(\Rightarrow x^2-4x-x^2-5x=-12\)
\(\Rightarrow-9x=-12\Rightarrow x=\frac{12}{9}\)
a) \(x\left(x-4\right)=x\left(x+5\right)-12\)
\(\Leftrightarrow x^2-4x=x^2+5x-12\)
\(\Leftrightarrow-9x=-12\)
\(\Leftrightarrow x=\frac{4}{3}\)
\(S=\left\{\frac{4}{3}\right\}\)
b) \(x^2+8=x\left(x-30\right)\)
\(\Leftrightarrow x^2+8=x^2-30x\)
\(\Leftrightarrow30x=-8\)
\(\Leftrightarrow=\frac{-4}{15}\)
\(S=\left\{\frac{-4}{15}\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(x+30\right)4=\left(x-30\right).5\)
\(4x+120=5x-150\)
\(120+150==5x-4x\)
\(270=x\)
(x + 30).4 = (x - 30).5
4x + 120 = 5x - 150
150 + 120 = 5x - 4x
=> x = 270