Bài 1:
a ) \(\dfrac{x}{5}=\dfrac{y}{7}\& x.y=140\)
b) \(\dfrac{x}{5}=\dfrac{y}{3}=\dfrac{z}{2} \& 3x-2y+7z=69\)
c) \(\dfrac{x}{5}=\dfrac{y}{4} \& x^2-y^2=1\)
d) \(5x=7y\&y-x=18\)
Giúp mk nhé :
Trần Thị Yến Nhi Phạm Hoàng Giang Nguyễn Huy Tú Ace Legona Akai Haruma
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