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...
Đọc tiếp
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
áp dụng tính chất của dãy tỉ số bằng nhau ta có :
\(\frac{3y+1}{12}\)=\(\frac{5y+2}{5x}\)=\(\frac{7y+3}{4x}\)=\(\frac{3y+1+7y+3}{12+4x}\)=\(\frac{4+10y}{12+4x}\)=\(\frac{2\left(2+5y\right)}{2\left(6+2x\right)}\)=\(\frac{2+5y}{6+2x}\)
\(\Leftrightarrow\)\(\frac{2+5y}{6+2x}\)=\(\frac{5y+2}{5x}\)
\(\Leftrightarrow\)6+2x=5x
\(\Leftrightarrow\)6=5x-2x=3x
\(\Leftrightarrow\)x=2
Thay x=2 vào \(\frac{5y+2}{5x}\) và \(\frac{7y+3}{4x}\) ta được:\(\frac{5y+2}{10}\)=\(\frac{7y+3}{8}\)
\(\Leftrightarrow\)8(5y+2)=10(7y+3)
\(\Leftrightarrow\)40y+16=70y+30
\(\Leftrightarrow\)40y-70y=30-16
\(\Leftrightarrow\)-30y=14
\(\Leftrightarrow\)y=\(\frac{-14}{30}\)
Vậy (x,y) là (2,\(\frac{-14}{30}\))