Question

a) tìm x,y biết :

 \(\frac{1+2y}{18}=\frac{1+4y}{24}=\frac{1+6y}{6x}\)

b) tìm x,y biết : x + y = x : y = 3 . ( x - y )

Giup mình

 

Answer 1

A ) ĐK: x#0 
Ta có:  
(1) 1+2y/18 = 1+4y/24 
=> 24 + 48y = 18 + 72y 
<=> y=1/4 
(2) 1+4y/24=1+6y/6x  
Thay y=1/4 vào (2) ta tìm đc x=5 (thỏa)

B ) x+y=3(x−y)=x:y
→x+y=3x−3y
→4y=2x
→x:y=4:2=2
→x+y=2
Mà x=2y nên
2y+y=3y=2
→y=2/3
→x=2−2/3=4/3

Chú ý : dấu / nghĩa là phần

Nếu mình đúng thì các bạn k mình nhé

Answer 2

a) \(\frac{1+2y}{18}=\frac{1+4y}{24}\Rightarrow24+48y=18+72y\Rightarrow6=24y\Rightarrow y=\frac{1}{4}\)

\(\frac{1+4y}{24}=\frac{1+6y}{6x}\Rightarrow\frac{1+4.\frac{1}{4}}{24}=\frac{1+6.\frac{1}{4}}{6x}\Rightarrow\frac{2}{24}=\frac{\frac{5}{2}}{6x}\Rightarrow12x=60\Rightarrow x=5\)

b) \(x+y=3\left(x-y\right)\Rightarrow x+y=3x-3y\Rightarrow4y=2x\Rightarrow x=2y\)

\(x+y=\frac{x}{y}\Rightarrow2y+y=\frac{2y}{y}\Rightarrow3y=2\Rightarrow y=\frac{2}{3}\Rightarrow x=2y=\frac{4}{3}\)

\(\)

Answer 3

a) \(\frac{1+2y}{18}=\frac{1+4y}{24}\) => (1+2y).24=18.(1+4y) => 24+48y=18+72y => y=\(\frac{1}{4}\)

=> \(\frac{1+6y}{6x}=\frac{1+6\cdot\frac{1}{4}}{6x}=\frac{\frac{5}{2}}{6x}=\frac{1+2\cdot\frac{1}{4}}{18}=\frac{1}{12}\)=> x= \(\frac{\frac{5}{2}\cdot12}{6}=5\)

b) x+y=3.(x-y) => x+y=3x-3y =>2x=4y => x/y=2 => x+y=3.(x-y)=2 => x-y=2/3

=> x=4/3; y=2/3