(3/(y-3)-2y/(9-y^2 )+y/(y+3))÷2y/(y+3)
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QD
3
8 tháng 12 2021
\(\dfrac{y}{y+3}-\dfrac{2y}{3-y}-\dfrac{3y^2+9}{y^2-9}=\dfrac{y\left(y-3\right)}{\left(y-3\right)\left(y+3\right)}+\dfrac{2y\left(y+3\right)}{\left(y-3\right)\left(y+3\right)}-\dfrac{3y^2+9}{\left(y-3\right)\left(y+3\right)}=\dfrac{y^2-3y+2y^2+6y-3y^2-9}{\left(y-3\right)\left(y+3\right)}=\dfrac{3y-9}{\left(y-3\right)\left(y+3\right)}=\dfrac{3\left(y-3\right)}{\left(y-3\right)\left(y+3\right)}=\dfrac{3}{y+3}\)
8 tháng 12 2021
\(=\dfrac{y^2-3y+2y^2+6y-3y^2+9}{\left(y-3\right)\left(y+3\right)}=\dfrac{3y+9}{\left(y-3\right)\left(y+3\right)}=\dfrac{3}{y-3}\)
28 tháng 7 2022
b: \(\left(x-\dfrac{2}{9}\right)^3=\left(\dfrac{y}{3}\right)^2=\left(\dfrac{2}{3}\right)^6\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left(x-\dfrac{2}{9}\right)^3=\left(\dfrac{4}{9}\right)^3\\\left(\dfrac{y}{3}\right)^2=\left(\dfrac{8}{27}\right)^2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x-\dfrac{2}{9}=\dfrac{4}{9}\\\dfrac{y}{3}=\dfrac{8}{27}\end{matrix}\right.\\\left\{{}\begin{matrix}x-\dfrac{2}{9}=\dfrac{4}{9}\\\dfrac{y}{3}=-\dfrac{8}{27}\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=\dfrac{2}{3}\\y=\dfrac{8}{9}\end{matrix}\right.\\\left\{{}\begin{matrix}x=\dfrac{2}{3}\\y=-\dfrac{8}{9}\end{matrix}\right.\end{matrix}\right.\)
c: =>8x-1=5
=>8x=6
hay x=3/4
15 tháng 7 2019
1)\(n^2\left(n-1\right)\left(n+1\right)-\left(n^2+2\right)\left(n^2-2\right)=n^2\left(n^2-1\right)-\left(n^4-4\right)=n^4-n^2-n^4+4\)
\(=-n^2+4\)
2)\(\left(y+3\right)\left(y-3\right)\left(y^2+9\right)-\left(y^2-4\right)\left(y^2+4\right)=\left(y^2-9\right)\left(y^2+9\right)-\left(y^4-16\right)\)
\(=y^4-81-y^4+16=-65\)
3)\(\left(x-2y+3\right)\left(x+2y-3\right)-\left(x-2y\right)\left(x+2y\right)=\left(x+3\right)^2-4y^2-\left(x^2-4y^2\right)\)
\(=x^2+6x+9-4y^2-x^2+4y^2=6x+9\)
4)\(\left(a+b+c\right)^2=a^2+b^2+c^2+2ab+2bc+2ac\)
5)\(\left(a+b-c\right)^2=a^2+b^2+c^2+2ab-2bc-2ac\)
6)\(\left(a-b-c\right)^2=a^2+b^2+c^2-2ab+2bc-2ac\)
Học tốt nha bạn !
H
25 tháng 6 2019
5,\(hpt\Leftrightarrow\left\{{}\begin{matrix}x\left(x+y\right)\left(x+2\right)=0\\2\sqrt{x^2-2y-1}+\sqrt[3]{y^3-14}=x-2\end{matrix}\right.\)
Thay từng TH rồi làm nha bạn
3,\(hpt\Leftrightarrow\left\{{}\begin{matrix}x-y=\frac{1}{x}-\frac{1}{y}=\frac{y-x}{xy}\\2y=x^3+1\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left(x-y\right)\left(1+\frac{1}{xy}\right)=0\\2y=x^3+1\end{matrix}\right.\)
thay nhá
T
3 tháng 11 2019
Bài 1:ĐKXĐ: \(2x\ge y;4\ge5x;2x-y+9\ge0\)\(\Rightarrow2x\ge y;x\le\frac{4}{5}\Rightarrow y\le\frac{8}{5}\)
PT(1) \(\Leftrightarrow\left(x-y-1\right)\left(2x-y+3\right)=0\)
+) Với y = x - 1 thay vào pt (2):
\(\frac{2}{3+\sqrt{x+1}}+\frac{2}{3+\sqrt{4-5x}}=\frac{9}{x+10}\) (ĐK: \(-1\le x\le\frac{4}{5}\))
Anh quy đồng lên đê, chắc cần vài con trâu đó:))
+) Với y = 2x + 3...
10 tháng 7 2023
a: A=2/3x^2y+4x^2y=14/3x^2y
=14/3*9*7=294
b: B=xy^2(1/2+1/3+1/6)=xy^2=3/4*1/4=3/16
c: C=x^3y^3(2+10-20)=-8x^3y^3
=-8*1^3(-1)^3=8
d: D=xy^2(2018+16-2016)
=18xy^2
=18(-2)*1/9=-4