Ta có :
`(x+2)^2=9`
`<=> (x+2)^2=+-3^2`
\(\Leftrightarrow\left[{}\begin{matrix}x+2=3\\x+2=-3\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-5\end{matrix}\right.\)
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`(y+3)^2=25`
`<=> (y+3)^2 =+-5^2`
\(\Leftrightarrow\left[{}\begin{matrix}y+3=5\\y+3=-5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}y=2\\y=-8\end{matrix}\right.\)
Giá trị `x/y` là : `1/2=4/8 ; (-5)/(-8)=5/8`
Vậy giá trị lớn nhất của `x/y` là `5/8`
`->C`
\(\left(x+2\right)^2=9\)
\(\Leftrightarrow\left(x+2\right)^2=3^2\)
\(\Leftrightarrow x+2=3\)
\(\Leftrightarrow x=1\)
\(\left(y+3\right)^2=25\)
\(\Leftrightarrow\left(y+3\right)^2=5^2\)
\(\Leftrightarrow y+3=5\)
\(\Leftrightarrow y=2\)
\(\Rightarrow\dfrac{x}{y}=\dfrac{1}{2}\)
Chọn A
