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\(\dfrac{x^3+8}{x^2+2x+1}.\dfrac{x^2+3x+2}{1-x^2}\left(x\ne\pm1\right)\\ =\dfrac{x^3+2^3}{\left(x+1\right)^2}.\dfrac{\left(x^2+x\right)+\left(2x+2\right)}{1^2-x^2}\\ =\dfrac{\left(x+2\right)\left(x^2-2x+4\right)}{\left(x+1\right)^2}.\dfrac{x\left(x+1\right)+2\left(x+1\right)}{\left(1-x\right)\left(1+x\right)}\\ =\dfrac{\left(x+2\right)\left(x^2-2x+4\right)}{\left(x+1\right)^2}.\dfrac{\left(x+2\right)\left(x+1\right)}{\left(1-x\right)\left(x+1\right)}\\ =\dfrac{\left(x+2\right)^2\left(x^2-2x+4\right)}{\left(1-x\right)\left(x+1\right)^2}\)
\(\left(2x-3\right)\left(2x+3\right)=2\left(2x-3\right)\left(2x-3\right)\)
\(\Leftrightarrow\left(2x-3\right)\left(2x+3\right)-2\left(2x-3\right)\left(2x-3\right)=0\)
\(\Leftrightarrow\left(2x-3\right)\left(2x+3-4x+6\right)=0\)
\(\Leftrightarrow\left(2x-3\right)\left(-2x+9\right)=0\)
\(\Leftrightarrow2x-3=0\) hay \(-2x+9=0\)
\(\Leftrightarrow x=\dfrac{3}{2}\) hay \(x=\dfrac{9}{2}\)
-Vậy \(S=\left\{\dfrac{3}{2};\dfrac{9}{2}\right\}\)
\(\left|2x-3\right|=3-2x\)
\(ĐK:x\le\dfrac{3}{2}\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-3=3-2x\\3-2x=3-2x\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\0=0\left(đúng\right)\end{matrix}\right.\)
Vậy \(S=\left\{x\in R;x=\dfrac{3}{2}\right\}\)
a: =(x-y)^2+2(x-y)
=(x-y)(x-y+2)
c: =(x-3)(x+3)+(x-3)^2
=(x-3)(x+3+x-3)
=2x(x-3)
d: =(x+3)(x^2-3x+9)-4x(x+3)
=(x+3)(x^2-7x+9)
e: =(x^2-8x+7)(x^2-8x+15)-20
=(x^2-8x)^2+22(x^2-8x)+85
=(x^2-8x+17)(x^2-8x+5)
a: \(\left(x-3\right)\left(2x^2-3x+4\right)\)
\(=2x^3-3x^2+4x-6x^2+9x-12\)
\(=2x^3-9x^2+13x-12\)
b: \(\left(4x^2y-5xy^2+6xy\right):2xy\)
\(=\dfrac{4x^2y-5xy^2+6xy}{2xy}\)
\(=\dfrac{2xy\cdot2x-2xy\cdot2,5y+2xy\cdot3}{2xy}\)
\(=2x-2,5y+3\)
c: \(\dfrac{x}{2x+4}-\dfrac{2}{x^3+2x}\)
\(=\dfrac{x\left(x^3+2x\right)-2\left(2x+4\right)}{x\left(x^2+2\right)\cdot2\cdot\left(x+2\right)}\)
\(=\dfrac{x^4+2x^2-4x-8}{2x\left(x^2+2\right)\left(x+2\right)}\)
a: \(=\dfrac{2\left(x+2\right)\left(x-1\right)}{x+2}=2x-2\)
b: \(=\dfrac{2x^3+x^2-6x^2-3x+2x+1}{2x+1}=x^2-3x+1\)
c: \(=\dfrac{x^3+2x^2-2x^2-4x+2x+4}{x+2}=x^2-2x+2\)
d: \(=\dfrac{x^2\left(x-3\right)}{x-3}=x^2\)
Lời giải:
$\frac{x^3+8}{x^2-2x+1}.\frac{x^2+3x+2}{1-x^2}=\frac{(x^3+8)(x^2+3x+2)}{(x^2-2x+1)(1-x^2)}$
$=\frac{(x+2)(x^2-2x+4)(x+1)(x+2)}{(x-1)^2(1-x)(x+1)}$
$=\frac{(x+2)^2(x^2-2x+4)}{-(x-1)^3}$
-x2(3-2x)=-3x2+2x3