(x+2)^2+(x-3)^2-2(x-1)(x+1)=9 =>x2+4x+4+x2-6x+9-2x2+2=9 =>(x2+x2-2x2)+(4x-6x)+4+9+2=9 =>-2x+15=9 =>-2x=-6 =>x=3

chu vi h.c.n la

(30+20)x2=100(m)

dien h h.c.n la

30x20=600(m2)

   dap so : chu vi : 100m

                dien h :600m2

đáp số: 770

k nha

a) TH1:

\(\left\{{}\begin{matrix}x< 0\\8-x>0\end{matrix}\right.\)\(\Rightarrow\left\{{}\begin{matrix}x< 0\\x< 8\end{matrix}\right.\) \(\Rightarrow x< 0\)

TH2:

\(\left\{{}\begin{matrix}x>0\\8-x< 0\end{matrix}\right.\)\(\Rightarrow\left\{{}\begin{matrix}x>0\\x>8\end{matrix}\right.\)\(\Rightarrow x>8\)

Vậy \(\left[{}\begin{matrix}x< 0\\x>8\end{matrix}\right.\)

b) TH1:

\(\left\{{}\begin{matrix}2-x>0\\x+3>0\end{matrix}\right.\)\(\Rightarrow\left\{{}\begin{matrix}x< 2\\x>-3\end{matrix}\right.\)\(\Rightarrow-3< x< 2\)

TH2:

\(\left\{{}\begin{matrix}2-x< 0\\x+3< 0\end{matrix}\right.\)\(\Rightarrow\left\{{}\begin{matrix}x>2\\x< -3\end{matrix}\right.\)(vô nghiệm)

Vậy \(-3< x< 2\)

c) TH1:

\(\left\{{}\begin{matrix}2x-4>0\\5-x< 0\end{matrix}\right.\)\(\Rightarrow\left\{{}\begin{matrix}2x>4\\x>5\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x>2\\x>5\end{matrix}\right.\Rightarrow x>5\)

TH2:

\(\left\{{}\begin{matrix}2x-4< 0\\5-x>0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}2x< 4\\x< 5\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x< 2\\x< 5\end{matrix}\right.\Rightarrow x< 2\)

Vậy \(\left[{}\begin{matrix}x>5\\x< 2\end{matrix}\right.\)

a. Đề:\(3\left(2x-1\right)^2+7\left(3y+5\right)^2=0\)

Giải :\(\Rightarrow\hept{\begin{cases}2x-1=0\\3y+5=0\end{cases}}\Rightarrow\hept{\begin{cases}2x=0+1=1\\3y=0-5=-5\end{cases}\Rightarrow\hept{\begin{cases}x=\frac{1}{2}\\y=-\frac{5}{3}\end{cases}}}\)

b. Đề : \(x^2+y^2-2x+10y+26=0\)

Giải : \(\Leftrightarrow x^2-2.1.x+1+y^2+2.5.y+25=0\)

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

\(\Leftrightarrow\hept{\begin{cases}x-1=0\\y+5=0\end{cases}\Leftrightarrow\hept{\begin{cases}x=0+1=1\\y=0-5=-5\end{cases}}}\)

Đây là bài 1 bài 2 đang ghi nha 

t i c k nha cảm ơn

\(\frac{8}{9}+\frac{1}{9}=\frac{8+1}{9}=\frac{9}{9}=1\)

3/8 <4/7

5/9<7/10

\(\frac{3}{4}=\frac{9}{12}\)

\(\frac{7}{6}=\frac{14}{12}\)

234+567+678+983+=2462

sao mình không thể tích cho bạn đứng được nhỉ , bạn làm bài cho mình rất rất rất đúng.