Question

[ZING ZING ZING]

Tìm y biết < y + 1/3 > +  < y + 1/9> +< y + 1/27 > + < y + 1/81 > = 56/81

Answer 1

[Bảo Ngọc]

\(\left(y+\frac{1}{3}\right)+\left(y+\frac{1}{9}\right)+\left(y+\frac{1}{27}\right)+\left(y+\frac{1}{81}\right)=\frac{56}{81}\)

\(\Leftrightarrow4y+\left(\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}\right)=\frac{56}{81}\)

\(\Leftrightarrow4y+\frac{40}{81}=\frac{56}{81}\)

\(\Leftrightarrow4y=\frac{56}{81}-\frac{40}{81}\)

\(\Leftrightarrow4y=\frac{16}{81}\)

\(\Rightarrow y=\frac{16}{81}\div4\)

\(\Rightarrow y=\frac{4}{81}\)

Vậy y có giá trị =\(\frac{4}{81}\)

Answer 2

[Ko Có Tên]

< y   1/3 >    < y   1/9>  < y   1/27 >   < y   1/81 > =  56 / 81   

= 4y + < 1/3 + 1/9 + 1/27 + 1/81 >  = 56 / 81

= 4y + 40 / 81 = 56 / 81 

= 4y = 56 / 81 - 40 / 81

= 4 / 81