rút gọn phân thức: x^2-3x phần x^2-6x+9
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`a,`
\(x^2-3x\ne0\)
`<=>x(x-3)`\(\ne0\)
\(\Leftrightarrow\left\{{}\begin{matrix}x\ne0\\x-3\ne0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x\ne0\\x\ne3\end{matrix}\right.\)
`b,`
đặt `A=(x^2-6x+9)/(x^2-3x)`
`A= ((x-3)^2)/(x(x-3))`
`A= (x-3)/x`
`c, `
để `x=5`
`=> A= (x -3)/x=(5-3)/5= 2/5`
\(\dfrac{2xy-x^2}{3x^3-6x^2y}\\ =\dfrac{x\left(2y-x\right)}{3x^2\left(x-2y\right)}\\ =\dfrac{x\left(2y-x\right)}{-3x^2\left(2y-x\right)}\\ =\dfrac{1}{-3x}\)
\(\dfrac{2xy-x^2}{3x^3-6x^2y}=\dfrac{-\left(x^2-2xy\right)}{3x^3-6x^2y}\)
\(=\dfrac{-x\left(x-2y\right)}{3x^2\left(x-2y\right)}=\dfrac{-1}{3x}\)
a: \(=\dfrac{3\left(x-2\right)}{\left(x-2\right)^3}=\dfrac{3}{\left(x-2\right)^2}\)
b: \(=\dfrac{x^2\left(x+2\right)}{\left(x+2\right)^3}=\dfrac{x^2}{\left(x+2\right)^2}\)
\(a,\frac{x^2-8x+15}{x^2-6x+9}\)
\(=\frac{\left(x-4\right)^2-1}{\left(x-3\right)^2}\)
\(=\frac{\left(x-3\right)\left(x-5\right)}{\left(x-3\right)^2}\)
\(=\frac{x-5}{x-3}\)
b) \(\frac{2x^2+3x-2}{x^2+x-2}\)
\(=\frac{2x^2-4x+x-2}{x^2+2x-x-2}\)
\(=\frac{2x\left(x-2\right)+\left(x-2\right)}{x\left(x+2\right)-\left(x+2\right)}\)
\(=\frac{\left(2x+2\right)\left(x-2\right)}{\left(x-1\right)\left(x+2\right)}\)
Bài 1:
Để B nguyên thì \(3x+1⋮x-1\)
\(\Leftrightarrow x-1\inƯ\left(4\right)\)
\(\Leftrightarrow x-1\in\left\{1;-1;2;-2;4;-4\right\}\)
hay \(x\in\left\{2;0;3;-1;5;-3\right\}\)
Bài 2:
a: Ta có: \(P=\dfrac{x^2-9}{x^2-6x+9}\)
\(=\dfrac{\left(x-3\right)\left(x+3\right)}{\left(x-3\right)^2}\)
\(=\dfrac{x+3}{x-3}\)
b: Để P nguyên thì \(x+3⋮x-3\)
\(\Leftrightarrow x-3\in\left\{1;-1;2;-2;3;-3;6;-6\right\}\)
hay \(x\in\left\{4;2;5;1;6;0;9;-3\right\}\)
\(P=\dfrac{3x^2+6x+3}{x+1}\)
\(a,\) Điều kiện xác định: \(x+1\ne0\Leftrightarrow x\ne-1\)
\(b,P=\dfrac{3x^2+6x+3}{x+1}=\dfrac{3\left(x^2+2x+1\right)}{x+1}=\dfrac{3\left(x+1\right)^2}{x+1}=3\left(x+1\right)=3x+3\)
\(c,x=1\Rightarrow P=3.1+3=6\)
\(\dfrac{x^2-3x}{x^2-6x+9}=\dfrac{x\left(x-3\right)}{\left(x-3\right)^2}=\dfrac{x}{x-3}.\)
ĐKXĐ: \(x\ne3.\)
\(=\dfrac{\left(x-3\right)\cdot x}{\left(x-3\right)^2}=\dfrac{x}{x-3}\)