:Ap dung tinh chat cua day ti so bang nhau ta co :

1+3y/12=1+5y/5x=1+7y/4x=1+7y-1-5y/4x-5x=2y/-x=1+5y-1-3y/5x-12=2y/5x-12

=>2y/-x=2y/5x-12 voi y=0 thay vao ko thoa man

neu y khac 0 

=>-x=5x-12=>x=2 . Thay x bang 2 vao tren ta dc : 

1+3y/12=2y/-2=-y=>1+3y=-12y=>1=-15y=>y=-1/15

Vay x=2,y=-1/15 thoa man de bai

ta xét 

\(\frac{1+3y}{12}\)= \(\frac{1+5y}{5x}\)

=> (1+3y)5x = (1+5y) 12 

=> 5x + 15xy = 12 + 60y 

=> 5x - 12 = 60y - 15xy 

=> 5x = 60y - 15xy + 12 

đén đây bn thay vào biểu thức còn lại rồi tính nhé 

+)Xét 2x-6lớn hơn hoặc bằng0

suy ra 2x-6+5x=9

suy ra 7x-6=9

suy ra 7x =15

suy ra x=15/7

+)Xét 2x-6<0

suy ra -2x+6+5x=9

suy ra 3x+6=9

suy ra 3x=3

suy ra x=1

nhớ bấm đúng cho mình nha

Đặt \(A=-1-\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-....-\frac{1}{1024}\)

\(=-\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{1024}\right)\)

Đặt \(B=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+....+\frac{1}{1024}\)

=> \(B=1+\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+...+\frac{1}{2^{10}}\)

=> \(2B=2+1+\frac{1}{2^2}+...+\frac{1}{2^9}\)

=> \(B=2B-B=2-\frac{1}{2^{10}}\)

=> \(A=-\left(2-\frac{1}{2^{10}}\right)=-\left(2-\frac{1}{1024}\right)=-\frac{2047}{1024}\)

\(\frac{a}{b}=\frac{c}{d}\)

\(\Leftrightarrow\frac{a}{b}+1=\frac{c}{d}+1\)

\(\Leftrightarrow\frac{a}{b}+\frac{b}{b}=\frac{c}{d}+\frac{d}{d}\)

\(\Rightarrow\frac{a+b}{b}=\frac{c+d}{d}\) (đpcm)

tui nè

hay ko? hjhj