Giải phương trình:
\(\frac{x^2+4x+6}{x+2}+\frac{x^2+16x+72}{x+8}=\frac{x^2+8x+20}{x+4}+\frac{x^2+12x+42}{x+6}\)
K
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P
2 tháng 1 2018
=>\(\frac{\left(x+2\right)^2+2}{x+2}+\frac{\left(x+8\right)^2+8}{x+8}\)=\(\frac{\left(x+4\right)+4}{x+4}+\frac{\left(x+6\right)^2+6}{x+6}\)
=>2x+10+\(\frac{2}{x+2}+\frac{8}{x+8}\)=2x+10+\(\frac{4}{x+4}+\frac{6}{x+6}\)
=>-x\(\left(\frac{1}{x+2}-\frac{1}{x+4}-\frac{1}{x+6}+\frac{1}{x+8}\right)\)=0
=>\(\orbr{\begin{cases}x=0\\\frac{1}{x+2}-.....+\frac{1}{x+8}=0\end{cases}}\)
Voi \(\frac{1}{x+2}-....\)=0 ta co
Dat x+5=t
=>\(\frac{1}{t-3}-\frac{1}{t-1}-\frac{1}{t+1}+\frac{1}{t+3}\)=0
=> \(2t\left(\frac{1}{t^2-1}+\frac{1}{t^2-9}\right)=0\)
=>t=0
=>x=-5
Vay phuong trinh co nghiem x=0;-5
G
27 tháng 3 2019
\(y^2+4^x+2y-2^{x+1}+2=0\)
\(\Leftrightarrow\left(y^2+2y+1\right)+\left(4^x-2^{x+1}+1\right)=0\)
\(\Leftrightarrow\left(y+1\right)^2+\left(2^x-1\right)^2=0\Leftrightarrow\hept{\begin{cases}y=-1\\x=0\end{cases}}\)
\(\frac{x^2+4x+6}{x+2}+\frac{x^2+16x+72}{x+8}=\frac{x^2+8x+20}{x+4}+\frac{x^2+12x+42}{x+6}\)
\(\Leftrightarrow\frac{x^2+4x+4+2}{x+2}+\frac{x^2+16x+64+8}{x+8}=\frac{x^2+8x+16+4}{x+4}+\frac{x^2+12x+36+6}{x+6}\)
\(\Leftrightarrow2x+10+\frac{2}{x+2}+\frac{8}{x+8}=2x+10+\frac{4}{x+4}+\frac{6}{x+6}\)
\(\Leftrightarrow\frac{2}{x+2}+\frac{8}{x+8}=\frac{4}{x+4}+\frac{6}{x+6}\)
Tới đây quy đồng làm tiếp nhé
NV
Nguyễn Việt Lâm
Giáo viên
14 tháng 4 2019
a/
\(\left(x^2+2x\right)\left(x^2+2x+2\right)+1=0\)
\(\Leftrightarrow\left(x^2+2x\right)^2+2\left(x^2+2x\right)+1=0\)
\(\Leftrightarrow\left(x^2+2x+1\right)^2=0\)
\(\Leftrightarrow x+1=0\)
\(\Rightarrow x=1\)
b/
\(y^2+2y+1+\left(2^x\right)^2-2.2^x+1=0\)
\(\Leftrightarrow\left(y+1\right)^2+\left(2^x-1\right)^2=0\)
\(\Leftrightarrow\left\{{}\begin{matrix}y+1=0\\2^x-1=0\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}y=-1\\x=0\end{matrix}\right.\)
c/
ĐKXĐ: \(x\ne\left\{-2;-4;-6;-8\right\}\)
\(\frac{\left(x+2\right)^2+2}{x+2}+\frac{\left(x+8\right)^2+8}{x+8}=\frac{\left(x+4\right)^2+4}{x+4}+\frac{\left(x+6\right)^2+6}{x+6}\)
\(\Leftrightarrow x+2+\frac{2}{x+2}+x+8+\frac{8}{x+8}=x+4+\frac{4}{x+4}+x+6+\frac{6}{x+6}\)
\(\Leftrightarrow\frac{1}{x+2}+\frac{4}{x+8}=\frac{2}{x+4}+\frac{3}{x+6}\)
\(\Leftrightarrow\frac{1}{x+2}-\frac{2}{x+4}+\frac{4}{x+8}-\frac{3}{x+6}=0\)
\(\Leftrightarrow\frac{-x}{\left(x+2\right)\left(x+4\right)}+\frac{x}{\left(x+8\right)\left(x+6\right)}=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\\frac{1}{\left(x+2\right)\left(x+4\right)}=\frac{1}{\left(x+6\right)\left(x+8\right)}\left(1\right)\end{matrix}\right.\)
\(\left(1\right)\Leftrightarrow\left(x+2\right)\left(x+4\right)=\left(x+6\right)\left(x+8\right)\)
\(\Leftrightarrow8x=-40\Rightarrow x=-5\)
14 tháng 7 2019
Sửa đề:
\(\frac{x^2+4x+6}{x+2}+\frac{x^2+16x+72}{x+8}=\frac{x^2+8x+20}{x+4}+\frac{x^2+12x+20}{x+6}\)
\(\Leftrightarrow\frac{\left(x+2\right)^2+2}{x+2}+\frac{\left(x+8\right)^2+8}{x+8}=\frac{\left(x+4\right)^2+4}{x+4}+\frac{\left(x+6\right)^2+6}{x+6}\)
\(\Leftrightarrow\frac{2}{x+2}+\frac{8}{x+8}=\frac{4}{x+4}+\frac{6}{x+6}\)
Quy đồng giải tiếp nhé
=> \(\frac{(x+2)^2+2}{x+2}+\frac{(x+8)^2+8}{x+8}=\frac{(x+4)+4}{x+4}+\frac{(x+6)^2+6}{x+6}\)
=> 2x + 10 + \(\frac{2}{x+2}+\frac{8}{x+8}=2x+10+\frac{4}{x+4}+\frac{6}{x+6}\)
=>-x \((\frac{1}{x+2}-\frac{1}{x+4}-\frac{1}{x+6}-\frac{1}{x+8})=0\)
\(x=0\)
\(=>\orbr{\frac{1}{x+2}}-.....+\frac{1}{x+8}=0\)
Với \(\frac{1}{x+2}-...=0\). Ta có :
Đặt x + 5 = t
=> \(\frac{1}{t-3}-\frac{1}{t-1}-\frac{1}{t+1}+\frac{1}{t+3}=0\)
\(=>2t(\frac{1}{t^2-1}+\frac{1}{t^2-9})=0\)
=> t = 0
=> x = -5
Vậy phương trình có nghiệm x= 0 ; - 5