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a: \(A=\left(\dfrac{1}{x-1}+\dfrac{x}{\left(x-1\right)\left(x^2+x+1\right)}\cdot\dfrac{x^2+x+1}{x+1}\right)\cdot\dfrac{\left(x+1\right)^2}{2x+1}\)
\(=\left(\dfrac{1}{x-1}+\dfrac{x}{\left(x-1\right)\left(x+1\right)}\right)\cdot\dfrac{\left(x+1\right)^2}{2x+1}\)
\(=\dfrac{x+1+x}{\left(x-1\right)\left(x+1\right)}\cdot\dfrac{\left(x+1\right)^2}{2x+1}\)
\(=\dfrac{2x+1}{x-1}\cdot\dfrac{x+1}{2x+1}=\dfrac{x+1}{x-1}\)
b: Thay x=1/2 vào A, ta được:
\(A=\dfrac{\dfrac{1}{2}+1}{\dfrac{1}{2}-1}=\dfrac{3}{2}:\dfrac{-1}{2}=-3\)
c: Để A là số nguyên thì \(x-1+2⋮x-1\)
\(\Leftrightarrow x-1\in\left\{1;-1;2;-2\right\}\)
\(\Leftrightarrow x\in\left\{2;0;3\right\}\)
\(a)\frac{x+2}{x+3}-\frac{5}{x^2+x-6}+\frac{1}{2-x}=\frac{-3}{4}\left(x\ne-3;x\ne2\right)\)
\(\Leftrightarrow\frac{x+2}{x+3}-\frac{5}{\left(x+3\right)\left(x-2\right)}-\frac{1}{x-2}=\frac{-3}{4}\)
\(\Leftrightarrow\frac{x^2-4}{\left(x-2\right)\left(x+3\right)}-\frac{5}{\left(x+3\right)\left(x-2\right)}-\frac{x+3}{\left(x-2\right)\left(x+3\right)}=\frac{-3}{4}\)
\(\Leftrightarrow\frac{x^2-4-5-x-3}{\left(x-2\right)\left(x+3\right)}=\frac{-3}{4}\)
\(\Leftrightarrow\frac{x^2-x-12}{\left(x-2\right)\left(x+3\right)}=\frac{-3}{4}\)
\(\Leftrightarrow\frac{\left(x-4\right)\left(x+3\right)}{\left(x-2\right)\left(x+3\right)}=\frac{-3}{4}\)
\(\Leftrightarrow\frac{x-4}{x-2}=\frac{-3}{4}\)
<=> 4x-16=-3x+6
<=> 4x-16+3x-6=0
<=> 7x-22=0
<=> 7x=22
<=> \(x=\frac{22}{7}\)(TMĐK)
P=x3+2x2-2x2-10x+10x+50+50-5x / 2x(x+5)
=x3+100-5x / 2x2+10x
=x3+100-1 / 2x2+2
đây là câu a nha ban mih ko ghi lai cái đề
\(b,\frac{3x-1}{x-1}-\frac{2x+5}{x+3}=1-\frac{4}{\left(x-1\right)\left(x+3\right)}\) \(\left(Đkxđ:\left\{{}\begin{matrix}x\ne1\\x\ne-3\end{matrix}\right.\right)\)
\(\Leftrightarrow\frac{3x-1}{x-1}-\frac{2x+5}{x+3}+\frac{4}{\left(x-1\right)\left(x+3\right)}=1\)
\(\Leftrightarrow\frac{\left(3x-1\right)\left(x+3\right)}{\left(x-1\right)\left(x+3\right)}-\frac{\left(2x+5\right)\left(x-1\right)}{\left(x-1\right)\left(x+3\right)}+\frac{4}{\left(x-1\right)\left(x+3\right)}=\frac{\left(x-1\right)\left(x+3\right)}{\left(x-1\right)\left(x+3\right)}\)
\(\Leftrightarrow\left(3x^2+8x-3\right)-\left(2x^2+3x-5\right)+4=x^2+2x-3\)
\(\Leftrightarrow x^2+5x+6=x^2+2x-3\)
\(\Leftrightarrow9=-3x\)
\(\Leftrightarrow x=-3\left(ktmđk\right)\)
\(\Leftrightarrow Ptvn\)
a, 2x-1 thuộc ước của 2,rồi giải ra
b,c tương tự
d\(\frac{x^2-64-123}{x+8}=\frac{\left(x+8\right)\left(x-8\right)-123}{x+8}=x-8-\frac{123}{X+8}\) .........rồi làm tương tự như câu a,,,,,,,,,,,,còn câu e cũng gần giống câu d
\(\Leftrightarrow\frac{5-2x}{3\left(3x-1\right)}+\frac{3\left(x^2-1\right)}{3\left(3x-1\right)}-\frac{\left(x+2\right)\left(1-3x\right)}{3\left(3x-1\right)}=0\)
\(\Rightarrow5-2x+3x^2-3-x+3x^2-2+6x=0\Leftrightarrow6x^2+3x=0\Leftrightarrow3x\left(2x+1\right)=0\Rightarrow\left[{}\begin{matrix}x=0\\x=-\frac{1}{2}\end{matrix}\right.\)
\(\Leftrightarrow-\frac{5x-2}{2\left(x-1\right)}+\frac{\left(2x-1\right)\left(x-1\right)}{2\left(x-1\right)}=\frac{1-x-x^2-x+3}{1-x}\Leftrightarrow\frac{2x^2-8x+3}{2\left(x-1\right)}=\frac{x^2+2x-4}{x-1}\)
\(\Rightarrow2x^2-8x+3=2x^2+4x-8\)\(\Leftrightarrow-8x+3=4x-8\Leftrightarrow-12x=-12\Rightarrow x=1\)
ĐK: x khác -1
\(\frac{2x-1}{x+1}=\frac{5\left(x+1\right)}{x+1}+\frac{3}{x+1}\)
\(\Leftrightarrow\frac{2x-1}{x+1}-\frac{5\left(x+1\right)}{x+1}-\frac{3}{x+1}=0\Leftrightarrow\frac{2x-1-5x-5-3}{x+1}=0=>\frac{-3x-9}{x+1}=-\frac{12}{x+1}=0\)
\(=>-3x-9=0=>x=-3\)
Có (2x-1)/(x+1)=5+3/(x+1) (2x-1)/(x+1)=5(x+1)/(x+1)+3/(x+1) Suy ra:2x-1=5(x+1)+3 2x-1=5x+5+3 2x-1=5x+8 2x-5x=8+1 -3x=9 x=-3