1) 52-|x-3|=80

<=> |x-3|=28

<=> x-3=28 hoặc x-3=-28

<=> x=31 hoặc x=-25

Đáp số x= 31 hoặc x=-25

2)  x*(x+2)=0

<=> x=0 hoặc x+2=0

<=> x=0 hoặc x=-2

vậy .......

1) 

 \(52-\left|x-3\right|=80\)

\(\Leftrightarrow\)\(\left|x-3\right|=52-80=-28\)

Vì \(\left|x-3\right|\ge0\)nên không tồn tại \(x\) thoả mãn đề bài 

2) 

\(x.\left(x+2\right)=0\)

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

Vậy \(x=0\)hoặc \(x=-2\)

3) 

\(\left(x-3\right).\left(4-x\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x-3=0\\4-x=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0+3=3\\x=4-0=4\end{cases}}}\)

Vậy \(x=3\)hoặc \(x=4\)

4) 

\(\left(-12\right).\left(x-5\right)+7.\left(3-x\right)=5\)

\(\Leftrightarrow\)\(\left(-12\right)x+60+21-7x=5\)

\(\Leftrightarrow\)\(\left(-12\right)x-7x=5-60-21\)

\(\Leftrightarrow\)\(x.\left(-12-7\right)=-76\)

\(\Leftrightarrow\)\(\left(-19\right)x=-76\)

\(\Rightarrow\)\(x=\frac{-76}{-19}=4\)

Vậy \(x=4\)

5) 

\(x^2=2x\)

\(\Leftrightarrow\)\(x^2:x=2\)

\(\Rightarrow\)\(x=2\)

Vậy \(x=2\)

Chúc bạn học tốt

a/ \(\left|3x-1\right|=\left|5-2x\right|\)

\(\Leftrightarrow\left[{}\begin{matrix}3x-1=5-2x\\3x-1=-5+2x\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}3x+2x=5+1\\3x-2x=-5+1\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}5x=6\\x=-4\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{6}{5}\\x=-4\end{matrix}\right.\)

Vậy ......

b/ \(\left|x+2\right|-\left|x+7\right|=0\)

\(\Leftrightarrow\left|x+2\right|=\left|x+7\right|\)

\(\Leftrightarrow\left[{}\begin{matrix}x+2=x+7\\x+2=-x-7\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x-x=7-2\\x+x=-7-2\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}0x=5\left(loại\right)\\2x=-9\end{matrix}\right.\)

\(\Leftrightarrow x=-\dfrac{9}{2}\)

Vậy ...............

c/ \(\left|2x-1\right|+x=2\)

\(\Leftrightarrow\left|2x-1\right|=2-x\)

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

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

\(\Leftrightarrow\left[{}\begin{matrix}3x=3\\x=-3\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-3\end{matrix}\right.\)

Vậy ..

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

\(\Rightarrow x-5=0\) vì \(x^2+1>0\)

\(\Rightarrow x=5\)

cAU 1 TƯƠNG TỰ NHÉ 

Tương tự sao được

a/ \(30.\left\{x+2+6\left(x-5\right)\right\}-24x=102\)

\(\Leftrightarrow30.\left\{x+2+6x-30\right\}-24x=102\)

\(\Leftrightarrow30.\left\{7x-28\right\}-24x=102\)

\(\Leftrightarrow210x-340-24x=102\)

\(\Leftrightarrow186x-340=102\)

\(\Leftrightarrow186x=442\)

\(\Leftrightarrow x=\frac{442}{186}\)

c/ \(\left(x+1\right)+\left(x+2\right)+....+\left(x+99\right)=0\)

\(\Leftrightarrow\left(x+x+...+x\right)+\left(1+2+......+99\right)=0\)

\(\Leftrightarrow99x+49500=0\)

\(\Leftrightarrow x=-50\)

thì mình bảo câu 1 làm tươgn tự nhé, còn câu 3 ko làm tương tự đc, hiểu ko bạn  Thanh Hằng Nguyễn

b) (x+1)^3-x(x-2)^2+x-1=0

 ⇔x^3+3x^2+3x+1-(x^3-4x^2+4x)=0

⇔ x^3+3x^2+3x+1-x^3+4x^2-4x+x-1=0

⇔7x^2-2=0

⇔7x^2=2

⇔7x^2=-2⇔x=-3

⇔7x^2=2⇔x=-căn 5

a: 3(x+7)-2x+5>0

=>3x+21-2x+5>0

=>x+26>0

=>x>-26

Sửa đề: \(\dfrac{x+2}{18}-\dfrac{x+3}{8}< \dfrac{x-1}{9}-\dfrac{x-4}{24}\)

=>\(\dfrac{4\left(x+2\right)}{72}-\dfrac{9\left(x+3\right)}{72}< \dfrac{8\left(x-1\right)}{72}< \dfrac{3\left(x-4\right)}{72}\)

=>\(4\left(x+2\right)-9\left(x+3\right)< 8\left(x-1\right)-3\left(x-4\right)\)

=>\(4x+8-9x-27< 8x-8-3x+12\)

=>-5x-19<5x+4

=>-10x<23

=>\(x>-\dfrac{23}{10}\)

b: \(3x+2+\left|x+5\right|=0\left(1\right)\)

TH1: x>=-5

(1) trở thành: 3x+2+x+5=0

=>4x+7=0

=>\(x=-\dfrac{7}{4}\left(nhận\right)\)

TH2: x<-5

=>x+5<0

=>|x+5|=-x-5

Phương trình (1) sẽ trở thành:

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

=>2x-3=0

=>2x=3

=>\(x=\dfrac{3}{2}\)