a) \(\left|x-1\right|+\left|x+3\right|=4\left(1\right)\)

+) TH1: Nếu \(x< -3\) thì \(x-1< 0;x+3< 0\)

\(\Rightarrow\left|x-1\right|=-x+1;\left|x+3\right|=-x-3\)

PT (1) trở thành: \(-x+1-x-3=4\)

\(\Leftrightarrow-2x=6\Leftrightarrow x=-3\left(loại\right)\)

+) TH2: Nếu \(-3\le x< 1\) thì \(x-1< 0;x+3>0\)

\(\Rightarrow\left|x-1\right|=-x+1;\left|x+3\right|=x+3\)

PT (1) trở thành: \(-x+1+x+3=4\)

\(\Leftrightarrow0x=0\) (luôn đúng)

Kết hợp với đk ta được: \(\Rightarrow-3\le x< 1\)

+) TH3: Nếu \(x\ge1\) thì \(x-1>0;x+3>0\)

\(\Rightarrow\left|x-1\right|=x-1;\left|x+3\right|=x+3\)

PT (1) trở thành: \(x-1+x+3=4\)

\(\Leftrightarrow2x=2\Leftrightarrow x=1\left(t/m\right)\)

Vậy x nằm trong khoảng \(-3\le x\le1.\)

Mấy bài kia làm tương tự.

2.

\(\left|x+1\right|+\left|x+2\right|+...+\left|x+10\right|=605x\)(1)

Vì các thừa số ở vế phải của (1) đều không âm nên x không âm. Do đó \(\left|x+1\right|+\left|x+2\right|+...+\left|x+10\right|=\left(x+1\right)+\left(x+2\right)+...+\left(x+10\right)\)

\(\Rightarrow\left(x+1\right)+\left(x+2\right)+...+\left(x+10\right)=605x\)

\(\Rightarrow10x+\dfrac{10\left(10+1\right)}{2}=605x\)

\(\Rightarrow55=595x\)

\(\Rightarrow x=\dfrac{55}{595}=\dfrac{11}{119}\)

Vậy x = \(\dfrac{11}{119}\)

2.

a) Ta có \(\left|3x-2019\right|=2019-3x\)

khi \(3x-2019< 0\)

\(\Leftrightarrow x< \dfrac{2019}{3}=673\)

Vậy \(x< 673.\)

b) Vì \(\left|x+1\right|\ge0\forall x;...\left|x+10\right|\ge0\forall x\)

\(\Rightarrow\left|x+1\right|+...+\left|x+10\right|\ge0\forall x\)

nên \(605x\ge0\Leftrightarrow x\ge0\)

\(\Rightarrow\left|x+1\right|=x+1;...\left|x+10\right|=x+10\)

Ta có: \(x+1+...+x+10=605x\)

\(\Rightarrow10x+55=605x\Rightarrow x=\dfrac{11}{119}\)

Vậy \(x=\dfrac{11}{119}.\)

\(a,121-\left(115+x\right)=3x-\left(25-9-5x\right)-8\\ 121-115-x=3x-25+9+5x-8\\ 6-x=8x-24\\ 8x+x=-24-6\\ 9x=-30\\ x=-\dfrac{30}{9}=-\dfrac{10}{3}\\ ----\\ b,2^{x+2}.3^{x+1}.5^x=10800\\ \left(2.3.5\right)^x.2^2.3=10800\\ 30^x.12=10800\\ 30^x=\dfrac{10800}{12}=900=30^2\\ Vậy:x=2\)

\(x-1=\sqrt[3]{2}+\sqrt[3]{4}\)

\(\Rightarrow\left(x-1\right)^3=6+3\sqrt[3]{8}\left(\sqrt[3]{2}+\sqrt[3]{4}\right)\)

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

\(\Rightarrow x^3-3x^2-3x-1=0\)

\(A=x^2\left(x^3-3x^2-3x-1\right)-x^4+4x^3-2x+2019\)

\(=-x\left(x^3-3x^2-3x-1\right)+x^3-3x^2-3x+2019\)

\(=1+2019=2020\)

d, \(\frac{x+1}{9}+\frac{x+2}{8}=\frac{x+3}{7}+\frac{x+4}{6}\)

\(\Leftrightarrow\frac{x+1}{9}+1+\frac{x+2}{8}+1=\frac{x+3}{7}+1+\frac{x+4}{6}+1\)

\(\Leftrightarrow\frac{x+10}{9}+\frac{x+10}{8}-\frac{x+10}{7}-\frac{x+10}{6}=0\)

\(\Leftrightarrow\left(x+10\right)\left(\frac{1}{9}+\frac{1}{8}-\frac{1}{7}-\frac{1}{6}\right)=0\)

\(\Leftrightarrow x+10=0\) (Vì \(\frac{1}{9}+\frac{1}{8}-\frac{1}{7}-\frac{1}{6}\) ≠ 0)

\(\Leftrightarrow x=-10\)

Vậy x = -10 là nghiệm của phương trình.

e, Đề sai.

Sửa đề: \(\frac{x}{2016}+\frac{x+1}{2017}+\frac{x+2}{2018}+\frac{x+3}{2019}+\frac{x+4}{2020}=5\)

\(\Leftrightarrow\frac{x}{2016}-1+\frac{x+1}{2017}-1+\frac{x+2}{2018}-1+\frac{x+3}{2019}-1+\frac{x+4}{2020}-1=0\)

\(\Leftrightarrow\frac{x-2016}{2016}+\frac{x-2016}{2017}+\frac{x-2016}{2018}+\frac{x-2016}{2019}+\frac{x-2016}{2020}=0\)

\(\Leftrightarrow\left(x-2016\right)\left(\frac{1}{2016}+\frac{1}{2017}+\frac{1}{2018}+\frac{1}{2019}+\frac{1}{2020}\right)=0\)

\(\Leftrightarrow x-2016=0\) (Vì \(\frac{1}{2016}+\frac{1}{2017}+\frac{1}{2018}+\frac{1}{2019}+\frac{1}{2020}\ne0\)

\(\Leftrightarrow x=2016\)

Vậy x = 2016 là nghiệm của phương trình.

1: Sửa đề: 2/x+2

\(\dfrac{2x+1}{x^2-4}+\dfrac{2}{x+2}=\dfrac{3}{2-x}\)

=>\(\dfrac{2x+1+2x-4}{x^2-4}=\dfrac{-3\left(x+2\right)}{\left(x-2\right)\left(x+2\right)}\)

=>4x-3=-3x-6

=>7x=-3

=>x=-3/7(nhận)

2: \(\Leftrightarrow\dfrac{\left(3x+1\right)\left(3-x\right)+\left(3+x\right)\left(1-3x\right)}{\left(1-3x\right)\left(3-x\right)}=2\)

=>9x-3x^2+3-x+3-9x+x-3x^2=2(3x-1)(x-3)

=>-6x^2+6=2(3x^2-10x+3)

=>-6x^2+6=6x^2-20x+6

=>-12x^2+20x=0

=>-4x(3x-5)=0

=>x=5/3(nhận) hoặc x=0(nhận)

3: \(\Leftrightarrow x\cdot\dfrac{8}{3}-\dfrac{2}{3}=1+\dfrac{5}{4}-\dfrac{1}{2}x\)

=>x*19/6=35/12

=>x=35/38

mọi người ơi câu b là giá trị tuyệt đối của x^2 -1 nha

giúp mình mình tick cho

a) \(\Leftrightarrow x^2+\dfrac{2}{3}x-x^2+\dfrac{3}{4}x=\dfrac{7}{12}\)

\(\Leftrightarrow\dfrac{17}{12}x=\dfrac{7}{12}\Leftrightarrow x=\dfrac{7}{17}\)

c) \(\Leftrightarrow\left[{}\begin{matrix}2x+1=-1\\2x+1=1\\2x+1=0\end{matrix}\right.\)

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

\(a,PT\Leftrightarrow3x^2+3x-2x^2-4x=-1-x\Leftrightarrow x^2=-1\left(\text{vô nghiệm}\right)\)

Vậy: ...

\(b,PT\Leftrightarrow4x\left(x-2019\right)-\left(x-2019\right)=0\Leftrightarrow\left(x-2019\right)\left(4x-1\right)=0\Leftrightarrow\left[{}\begin{matrix}x=2019\\x=\dfrac{1}{4}\end{matrix}\right.\)

Vậy: ...

\(c,PT\Leftrightarrow\left(x-4-6\right)\left(x-4+6\right)=0\Leftrightarrow\left(x-10\right)\left(x+2\right)=0\Leftrightarrow\left[{}\begin{matrix}x=10\\x=-2\end{matrix}\right.\)

Vậy: ...

\(d,PT\Leftrightarrow\left(x+4\right)^2=0\Leftrightarrow x=-4\)

Vậy: ...

\(e,PT\Leftrightarrow x\left(x+6\right)-7\left(x+6\right)=0\Leftrightarrow\left(x+6\right)\left(x-7\right)=0\Leftrightarrow\left[{}\begin{matrix}x=-6\\x=7\end{matrix}\right.\)

Vậy: ...

\(f,PT\Leftrightarrow\left(5x-3\right)\left(5x+3\right)=0\Leftrightarrow x=\pm\dfrac{3}{5}\)

Vậy: ...

Bài 1.