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qui dao
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Nguyễn Việt Lâm
14 tháng 2 2022 lúc 22:10

ĐKXĐ: \(\left[{}\begin{matrix}x>1\\x< -1\end{matrix}\right.\)

- Với \(x=-\dfrac{3}{2}\) là nghiệm của BPT

- Với \(x>-\dfrac{3}{2}\Rightarrow2x+3>0\)

\(\Rightarrow\dfrac{3\left(2x-3\right)\left(2x+3\right)}{\sqrt{3x^2-3}}\le2x+3\)

\(\Leftrightarrow\dfrac{3\left(2x-3\right)}{\sqrt{3x^2-3}}\le1\)

\(\Rightarrow3\left(2x-3\right)\le\sqrt{3x^2-3}\)

\(\Leftrightarrow\left[{}\begin{matrix}2x-3< 0\\\left\{{}\begin{matrix}2x-3\ge0\\9\left(2x-3\right)^2\le3x^2-3\end{matrix}\right.\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}-\dfrac{3}{2}< x< \dfrac{3}{2}\\\left[{}\begin{matrix}x\ge\dfrac{3}{2}\\11x^2-36x+28\le0\end{matrix}\right.\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}-\dfrac{3}{2}< x< \dfrac{3}{2}\\\left\{{}\begin{matrix}x\ge\dfrac{3}{2}\\\dfrac{14}{11}\le x\le2\end{matrix}\right.\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}-\dfrac{3}{2}< x< \dfrac{3}{2}\\\dfrac{3}{2}\le x\le2\end{matrix}\right.\) \(\Rightarrow-\dfrac{3}{2}< x\le2\)

Kết hợp ĐKXĐ \(\Rightarrow\left[{}\begin{matrix}-\dfrac{3}{2}< x< -1\\1< x\le2\end{matrix}\right.\)

- Với \(x< -\dfrac{3}{2}\Rightarrow2x+3< 0\)

\(\dfrac{3\left(2x-3\right)\left(2x+3\right)}{\sqrt{3x^2-3}}\le2x+3\Leftrightarrow\dfrac{3\left(2x-3\right)}{\sqrt{3x^2-3}}\ge1\)

\(\Rightarrow3\left(2x-3\right)\ge\sqrt{3x^2-3}\)

Do \(x< -\dfrac{3}{2}\Rightarrow3\left(2x-3\right)< 0\Rightarrow\) BPT vô nghiệm

Vậy nghiệm của BPT là \(\left[{}\begin{matrix}-\dfrac{3}{2}\le x< -1\\1< x\le2\end{matrix}\right.\)

Lê Thu Trang
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Thu Nguyen
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Mộc Miên
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Thiện Nguyễn
25 tháng 3 2020 lúc 9:56
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Thiện Nguyễn
25 tháng 3 2020 lúc 9:54
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Thiện Nguyễn
25 tháng 3 2020 lúc 9:55
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Nguyễn Thế Mãnh
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Nguyễn Việt Lâm
28 tháng 2 2020 lúc 12:34

ĐKXĐ: \(-1\le x\le2\)

\(\Leftrightarrow2x^2-2x-1+\sqrt{\left(x+1\right)\left(2-x\right)}\le0\)

Đặt \(\sqrt{\left(x+1\right)\left(2-x\right)}=t\ge0\)

\(\Rightarrow2x^2-2x=4-2t^2\)

BPT trở thành:

\(4-2t^2-1+t\le0\Leftrightarrow-2t^2+t+3\le0\Rightarrow\left[{}\begin{matrix}t\le-1\left(l\right)\\t\ge\frac{3}{2}\end{matrix}\right.\)

\(\Rightarrow\left(x+1\right)\left(2-x\right)\ge\frac{9}{4}\)

\(\Leftrightarrow x^2-x+\frac{1}{4}\le0\Rightarrow x=\frac{1}{2}\)

Vậy BPT có nghiệm duy nhất \(x=\frac{1}{2}\)

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tl:)
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Thanh Hoàng Thanh
14 tháng 1 2022 lúc 20:23

\(1.\dfrac{x-1}{3}-x=\dfrac{2x-4}{4}.\Leftrightarrow\dfrac{x-1-3x}{3}=\dfrac{x-2}{2}.\Leftrightarrow\dfrac{-2x-1}{3}-\dfrac{x-2}{2}=0.\)

\(\Leftrightarrow\dfrac{-4x-2-3x+6}{6}=0.\Rightarrow-7x+4=0.\Leftrightarrow x=\dfrac{4}{7}.\)

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

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

\(\Leftrightarrow\left[{}\begin{matrix}x=2.\\x=1.\end{matrix}\right.\)

\(3.3x^2-4x+1=0.\Leftrightarrow\left(x-1\right)\left(x-\dfrac{1}{3}\right)=0.\Leftrightarrow\left[{}\begin{matrix}x=1.\\x=\dfrac{1}{3}.\end{matrix}\right.\)

\(4.\left|2x-4\right|=0.\Leftrightarrow2x-4=0.\Leftrightarrow x=2.\)

\(5.\left|3x+2\right|=4.\Leftrightarrow\left[{}\begin{matrix}3x+2=4.\\3x+2=-4.\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}.\\x=-2.\end{matrix}\right.\)

ILoveMath
14 tháng 1 2022 lúc 20:26

\(1,\dfrac{x-1}{3}-x=\dfrac{2x-4}{4}\\ \Leftrightarrow\dfrac{x-1}{3}-x=\dfrac{x-2}{2}\\ \Leftrightarrow\dfrac{2\left(x-1\right)-6x}{6}=\dfrac{3\left(x-2\right)}{6}\\ \Leftrightarrow2\left(x-1\right)-6x=3\left(x-2\right)\\ \Leftrightarrow2x-2-6x=3x-6\\ \Leftrightarrow-4x-2=3x-6\)

\(\Leftrightarrow3x-6+4x+2=0\\ \Leftrightarrow7x-4=0\\ \Leftrightarrow x=\dfrac{4}{7}\)

\(2,\left(x-2\right)\left(2x-1\right)=x^2-2x\\ \Leftrightarrow2x^2-4x-x+2=x^2-2x\\ \Leftrightarrow x^2-3x+2=0\\ \Leftrightarrow\left(x^2-2x\right)-\left(x-2\right)=0\\ \Leftrightarrow x\left(x-2\right)-\left(x-2\right)=0\\ \Leftrightarrow\left(x-1\right)\left(x-2\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=1\\x=2\end{matrix}\right.\)

\(3,3x^2-4x+1=0\\ \Leftrightarrow\left(3x^2-3x\right)-\left(x-1\right)=0\\ \Leftrightarrow3x\left(x-1\right)-\left(x-1\right)=0\\ \Leftrightarrow\left(x-1\right)\left(3x-1\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=1\\x=\dfrac{1}{3}\end{matrix}\right.\)

\(4,\left|2x-4\right|=0\\ \Leftrightarrow2x-4=0\\ \Leftrightarrow2x=4\\ \Leftrightarrow x=2\)

\(5,\left|3x+2\right|=4\\ \Leftrightarrow\left[{}\begin{matrix}3x+2=4\\3x+2=-4\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}3x=2\\3x=-6\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=-2\end{matrix}\right.\)

\(6,\left|2x-5\right|=\left|-x+2\right|\\ \Leftrightarrow\left[{}\begin{matrix}2x-5=-x+2\\2x-5=x-2\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}3x=7\\x=3\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{7}{3}\\x=3\end{matrix}\right.\)

Hi Mn
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Đinh Diệp
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Mysterious Person
15 tháng 9 2018 lúc 13:31

a) ta có : \(3x-5>2\left(x-1\right)+x\Leftrightarrow3x-5>2x-2+x\)

\(\Leftrightarrow-5>-2\left(vôlí\right)\) \(\Rightarrow x\in\varnothing\)

b) ta có : \(\left(x+2\right)^2-\left(x-2\right)^2>8x-2\Leftrightarrow8x>8x-2\)

\(\Leftrightarrow0>-2\left(đúng\forall x\right)\) \(\Rightarrow x\in R\)

c) ta có : \(3\left(4x+1\right)-2\left(5x+2\right)\ge8x-2\)

\(\Leftrightarrow12x+3-10x-4\ge8x-2\Leftrightarrow-6x\ge-1\Leftrightarrow x\le\dfrac{1}{6}\)

d) ta có : \(2x^2+2x+1-\dfrac{15\left(x+1\right)}{2}\le2x\left(x+1\right)\)

\(\Leftrightarrow2x^2+2x+\dfrac{2-15x-15}{2}\le2x^2+2x\)

\(\Rightarrow\dfrac{-15x-13}{2}\le0\Leftrightarrow-15x-13\le0\Leftrightarrow x\ge\dfrac{-13}{15}\)

Cam Anh
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