x + 20 = 60 : 2
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\(\dfrac{60}{x}-\dfrac{60}{x+20}=\dfrac{1}{2}\left(đk:x>0\right)\)
\(\Leftrightarrow\dfrac{120\left(x+20\right)-120x-x\left(x+20\right)}{2x\left(x+20\right)}=0\)
\(\Leftrightarrow120x+2400-120x-x^2-20x=0\)
\(\Leftrightarrow-x^2-20x+2400=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x_1=40\left(n\right)\\x_2=-60\left(l\right)\end{matrix}\right.\)
Vậy \(S=\left\{40\right\}\)
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\(\dfrac{60}{x}-\dfrac{60}{x+2}=\dfrac{1}{20}\left(đk:x\ne0,x\ne-2\right)\)
\(\Leftrightarrow\dfrac{60x+120-60x}{x\left(x+2\right)}=\dfrac{1}{20}\)
\(\Leftrightarrow\dfrac{120}{x^2+2x}=\dfrac{1}{20}\Leftrightarrow x^2+2x=2400\)
\(\Leftrightarrow\left(x+1\right)^2=2401\)
\(\Leftrightarrow\left[{}\begin{matrix}x+1=49\\x+1=-49\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=48\\x=-50\end{matrix}\right.\)(thỏa đk)
Ta có: \(\dfrac{60}{x}-\dfrac{60}{x+2}=\dfrac{1}{20}\)
\(\Leftrightarrow x\left(x+2\right)=1200x+2400-1200x\)
\(\Leftrightarrow x^2+2x-2400=0\)
\(\Delta=2^2-4\cdot1\cdot\left(-2400\right)=9604\)
Vì \(\Delta>0\) nên phương trình có hai nghiệm phân biệt là:
\(\left\{{}\begin{matrix}x_1=\dfrac{-2-98}{2}=-50\left(nhận\right)\\x_2=\dfrac{-2+98}{2}=48\left(nhận\right)\end{matrix}\right.\)
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a/ 35l + 18l = 53l 53l - 35l = 18l 53l - 18l = 35l
b/ 5 kg x 2 = 10 kg 10 kg : 2 = 5 kg 10 kg : 5 = 2 kg
c/ 40 m + 20 m = 60 m 60 m - 20 m = 40 m 60 m - 40 m = 20 m
a) 35l+18l=53l 53l-35l=18l 53l-18l=35l
b)5kgx2=10kg 10kg:2=5kg 10kg:5=2kg
c)40m+20m=60m 60m-20m=40m 60m-40m=20m
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x + 20 = 60 : 2
x + 20 = 30
x = 30 - 20
x = 10
kết bạn và k cho mik nhé
x + 20 = 60 : 2
x + 20 = 30
x = 30 - 20
x = 10
tk mk mk tk lại