tim x dua vao quan he uoc boi:tim so tu nhien x sao cho x-1 la uoc cua 12tim so tu nhien x sao cho 2x+1 la uoc cua 28tim so tu nhien x sao cho x+15 la boi cua x+3tim cac so nguyen x,y sao cho (x+1)(y-2)=3tim so nguyen x sao cho(x+2).(y-1)=2tim so nguyen to x vua la uoc cua 275 vua la uoc cua 180tim so nguyen to x,y biet x+y=12 va UCLL (x:y)=5tim so tu nhien x,y biet x+y=32 va UCLL (x:y)=8tim so tu nhien x biet x chia het cho10; xchia het cho12; x chia het cho15 va 100<x<150tim so x nho nhat khac 0b...
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tim x dua vao quan he uoc boi:
tim so tu nhien x sao cho x-1 la uoc cua 12
tim so tu nhien x sao cho 2x+1 la uoc cua 28
tim so tu nhien x sao cho x+15 la boi cua x+3
tim cac so nguyen x,y sao cho (x+1)(y-2)=3
tim so nguyen x sao cho(x+2).(y-1)=2
tim so nguyen to x vua la uoc cua 275 vua la uoc cua 180
tim so nguyen to x,y biet x+y=12 va UCLL (x:y)=5
tim so tu nhien x,y biet x+y=32 va UCLL (x:y)=8
tim so tu nhien x biet x chia het cho10; xchia het cho12; x chia het cho15 va 100<x<150
tim so x nho nhat khac 0b biet x chia het cho 24 va 30
40 chia het cho x . 56 chia het cho x va x>6
Ta có :
\(\frac{x}{x+y-2}=\frac{y}{x+z+3}=\frac{z}{x+y-5}=x+y+z.\)
Áp dụng tính chất dãy tỉ số bằng nhau ta có :
\(\frac{x}{x+y-2}=\frac{y}{x+z+3}=\frac{z}{x+y-5}=x+y+z.\)
\(\Leftrightarrow\frac{x+y+z}{x+y-2+x+z+3+x+y-5}=x+y+z\)
\(\Leftrightarrow\frac{x+y+z}{2x+2y+2z-4}=x+y+z\)
\(\Leftrightarrow2.\left(x+y+z-2\right)=1\)
\(\Leftrightarrow x+y+z-2=\frac{1}{2}\)
\(\Leftrightarrow x+y+z=\frac{1}{2}+2=\frac{5}{2}\)
Ta có :
\(\frac{x}{x+y-2}=\frac{y}{x+z+3}=\frac{z}{x+y-5}=x+y+z.\)
Áp dụng tính chất dãy tỉ số bằng nhau ta có :
\(\frac{x}{x+y-2}=\frac{y}{x+z+3}=\frac{z}{x+y-5}=x+y+z.\)
\(\Leftrightarrow\frac{x+y+z}{x+y-2+x+z+3+x+y-5}=x+y+z\)
\(\Leftrightarrow\frac{x+y+z}{2x+2y+2z-4}=x+y+z\)
\(\Leftrightarrow2.\left(x+y+z-2\right)=1\)
\(\Leftrightarrow x+y+z-2=\frac{1}{2}\)
\(\Leftrightarrow x+y+z=\frac{1}{2}+2=\frac{5}{2}\)