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31 tháng 7 2019

\(x^2-2x+3=t\left(t\ge0\right)\)

\(pt\Leftrightarrow\frac{1}{t-1}+\frac{1}{t}=\frac{9}{2\left(t+1\right)}\)

\(\Leftrightarrow\frac{2t\left(t+1\right)}{2t\left(t^2-1\right)}+\frac{2\left(t^2-1\right)}{2t\left(t^2-1\right)}-\frac{9t\left(t-1\right)}{2t\left(t^2-1\right)}=0\)

\(\Leftrightarrow-5t^2+11t-2=0\)

\(\Leftrightarrow\left(5x-1\right)\left(x-2\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x=\frac{1}{5}\\x=2\end{cases}}\)

28 tháng 3 2020

a) ĐKXĐ: x khác +2

\(\frac{x-2}{2+x}-\frac{3}{x-2}-\frac{2\left(x-11\right)}{x^2-4}\)

<=> \(\frac{x-2}{2+x}-\frac{3}{x-2}=\frac{2\left(x-11\right)}{\left(x-2\right)\left(x+2\right)}\)

<=> (x - 2)^2 - 3(2 + x) = 2(x - 11)

<=> x^2 - 4x + 4 - 6 - 3x = 2x - 22

<=> x^2 - 7x - 2 = 2x - 22

<=> x^2 - 7x - 2 - 2x + 22 = 0

<=> x^2 - 9x + 20 = 0

<=> (x - 4)(x - 5) = 0

<=> x - 4 = 0 hoặc x - 5 = 0

<=> x = 4 hoặc x = 5

làm nốt đi 

30 tháng 7 2016

Đề đúng : Chứng minh : \(\frac{x^4+4}{x\left(x^2+2\right)-2x^2-\left(x-1\right)^2-1}=\frac{x^2+2x+2}{x-1}\)

Điều kiện : \(x\ne1\)

Phân tích : \(x^4+4=\left(x^4+4x^2+4\right)-4x^2=\left(x^2+2\right)^2-\left(2x\right)^2=\left(x^2-2x+2\right)\left(x^2+2x+2\right)\)

\(x\left(x^2+2\right)-2x^2-\left(x-1\right)^2-1=x^3+2x-2x^2-\left(x^2-2x+1\right)-1\)

\(=x^3-3x^2+4x-2=\left(x^3-3x^2+3x-1\right)+\left(x-1\right)=\left(x-1\right)^3+\left(x-1\right)\)

\(=\left(x-1\right)\left(x^2-2x+2\right)\)

Suy ra : \(\frac{x^4+4}{x\left(x^2+2\right)-2x^2-\left(x-1\right)^2-1}=\frac{\left(x^2-2x+2\right)\left(x^2+2x+2\right)}{\left(x-1\right)\left(x^2-2x+2\right)}=\frac{x^2+2x+2}{x-1}\)

28 tháng 1 2020

\(ĐKXĐ:x\ne\pm5\)

 \(\frac{3}{4\left(x-5\right)}+\frac{15}{50-2x^2}=\frac{-7}{6\left(x+5\right)}\)

\(\Rightarrow\frac{3\left(x+5\right)}{4\left(x-5\right)\left(x+5\right)}+\frac{30}{4\left(25-x^2\right)}=\frac{-7\left(x-5\right)}{6\left(x+5\right)\left(x-5\right)}\)

\(\Rightarrow\frac{3x+15}{4\left(x-5\right)\left(x+5\right)}+\frac{-30}{4\left(x-5\right)\left(x+5\right)}=\frac{-7\left(x-5\right)}{6\left(x+5\right)\left(x-5\right)}\)

\(\Rightarrow\frac{3x+15-30}{4\left(x-5\right)\left(x+5\right)}=\frac{-7\left(x-5\right)}{6\left(x+5\right)\left(x-5\right)}\)

\(\Rightarrow\frac{3x-15}{4\left(x-5\right)\left(x+5\right)}=\frac{-7\left(x-5\right)}{6\left(x+5\right)\left(x-5\right)}\)

\(\Rightarrow\frac{3\left(x-5\right)}{4\left(x-5\right)\left(x+5\right)}=\frac{-7\left(x-5\right)}{6\left(x+5\right)\left(x-5\right)}\)

\(\Rightarrow\frac{3}{4\left(x+5\right)}=\frac{-7}{6\left(x+5\right)}\)

\(\Rightarrow18\left(x+5\right)=-28\left(x+5\right)\)

\(\Rightarrow18\left(x+5\right)+28\left(x+5\right)=0\)

\(\Rightarrow46\left(x+5\right)=0\Leftrightarrow x+5=0\Leftrightarrow x=-5\)(ktm)

Vậy pt vô nghiệm

10 tháng 3 2020

a,\(\left(3x-2\right)\left(x+6\right)\left(x^2+5\right)=0\)

Ta có: \(x^2+5\ge0\) (vô lí)

\(\Leftrightarrow\orbr{\begin{cases}3x-2=0\\x+6=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{2}{3}\\x=-6\end{cases}}\)

Vậy ....

c, \(4x^2\left(x-1\right)-x+1=0\)

\(\Leftrightarrow4x^3-4x^2-x+1=0\)

\(\Leftrightarrow4x^2\left(x-1\right)-\left(x-1\right)=0\)

\(\Leftrightarrow\left(4x^2-1\right)\left(x-1\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}4x^2-1=0\\x-1=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}4x^2=1\\x=1\end{cases}}\Leftrightarrow\orbr{\begin{cases}x^2=\frac{1}{4}\\x=1\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\pm\frac{1}{2}\\x=1\end{cases}}\)

Vậy ....

10 tháng 3 2020

\(\frac{x+2}{x+3}-\frac{x+1}{x-1}=\frac{4}{\left(x-1\right)\left(x+3\right)}\)

ĐKXĐ: \(x\ne1,x\ne-3\)

PT đã cho \(\Leftrightarrow\frac{\left(x+2\right).\left(x-1\right)-\left(x+1\right).\left(x+3\right)}{\left(x+3\right).\left(x-1\right)}=\frac{4}{\left(x-1\right)\left(x+3\right)}\)

\(\Leftrightarrow\frac{\left(x+2\right).\left(x-1\right)-\left(x+1\right).\left(x+3\right)}{\left(x+3\right).\left(x-1\right)}=\frac{4}{\left(x-1\right)\left(x+3\right)}\)

\(\Rightarrow x^2+x-2-x^2-4x-3=4\Leftrightarrow3x=-1\Leftrightarrow x=\frac{-1}{3}\)

10 tháng 5 2017

Câu 1:

a)\(x^2-4+\left(x-2\right)\left(2x+1\right)=0\)

\(\Rightarrow x^2-4+2x^2+x-4x-2=0\)

\(\Rightarrow3x^2-3x-6=0\)

\(\Rightarrow x^2-x-2=0\)(Vì nhân tử chung là 3 thì ra bằng 0)

\(\Rightarrow x^2-2x+x-2=0\)

\(\Rightarrow\left(x+1\right)\left(x-2\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x+1=0\\x-2=0\end{cases}\Rightarrow}\orbr{\begin{cases}x=-1\\x=2\end{cases}}\)

         Vậy x=-1;2

Câu 2:

a)\(ĐKXĐ:X\ne1;X\ne-1;X\ne-2;\)

b)\(\frac{x+1}{x-1}-\frac{x-1}{x+2}=\frac{3}{x^2-1}\)(\(ĐKXĐ:X\ne1;X\ne-1;X\ne-2;\))

\(\Rightarrow\frac{\left(x+1\right)^2\left(x+2\right)}{\left(x^2-1\right)\left(x+2\right)}-\frac{\left(x+1\right)\left(x-1^{ }\right)^2}{\left(x^2-1\right)\left(x+2\right)}=\frac{3\left(x+2\right)}{\left(x^2-1\right)\left(x+2\right)}\)

\(\Rightarrow\left(x+1\right)^2\left(x+2\right)-\left(x+1\right)\left(x-1\right)^2=3x+6\)

\(\Rightarrow\left(x+1\right)\left[\left(x+1\right)\left(x+2\right)-\left(x-1\right)^2\right]=3x+6\)

\(\Rightarrow\left(x+1\right)\left[x^2+3x+2-x^2+2x-1\right]=3x+6\)

\(\Rightarrow\left(x+1\right)\left[5x+1\right]=3x+6\)

\(\Rightarrow5x^2+6x+1-3x-6=0\)

\(\Rightarrow5x^2+3x-5=0\)

\(\Rightarrow x=0,745\left(TM\right)\)

10 tháng 5 2017

a)Ta có:\(1-2x=\frac{-7x-11}{5}\)

\(\Rightarrow\frac{5-10x}{5}=\frac{-7x-11}{5}\)

\(\Rightarrow5-10x=-7x-11\)

\(\Rightarrow5-10x+7x+11=0\)

\(\Rightarrow16-3x=0\)

\(\Rightarrow x=\frac{16}{3}\)

  

26 tháng 2 2022

hic, mk chx học

6 tháng 1 2019

Bạn chắc bạn viết đúng đề bài không?

15 tháng 1 2019

a, \(\frac{\left(x-2\right)^2}{3}-\frac{\left(2x-3\right).\left(2x+3\right)}{8}+\frac{\left(x-4\right)^2}{6}=0\)

\(\Leftrightarrow\frac{x^2-4x+4}{3}+\frac{9-4x^2}{8}+\frac{x^2-8x+16}{6}=0\)

\(\Leftrightarrow\frac{8\left(x^2-4x+4\right)+3\left(9-4x^2\right)+4\left(x^2-8x+16\right)}{24}=0\)

\(\Leftrightarrow\frac{8x^2-32x+32+27-12x^2+4x^2-32x+64}{24}=0\)

\(\Leftrightarrow\frac{123-64x}{24}=0\Leftrightarrow123-64x=0\Leftrightarrow x=\frac{123}{64}\)