Question

 Tìm y biết \(\left(\frac{1}{2x4}+\frac{1}{4x6}+\frac{1}{6x8}+\frac{1}{8x10}\right).y=\frac{1}{3}\)

Answer 1

\(\left(\frac{1}{2.4}+\frac{1}{4.6}+\frac{1}{6.8}+\frac{1}{8.10}\right).y=\frac{1}{3}\)

\(\frac{1}{2}\left(\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+\frac{2}{8.10}\right).y=\frac{1}{3}\)

\(\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+\frac{1}{8}-\frac{1}{10}\right).y=\frac{1}{3}:\frac{1}{2}=\frac{2}{3}\)

\(\left(\frac{1}{2}-\frac{1}{10}\right).y=\frac{2}{3}\)

\(\frac{2}{5}.y=\frac{2}{3}\)

=> \(y=\frac{2}{3}:\frac{2}{5}\)

=>\(y=\frac{3}{5}\)

Answer 2

sao ra 1phan 3

Answer 3

sao ra 1/2

Answer 4

sai ra 5/3

Answer 5

(1/2x4+1/4x6+1/6x8+1/8x10)x y =1/3

(1/8+1/24+1/48+1/80) x Y=1/3

(6/48+2/48+1/48+1/80)x Y =1/3

             3/16             +1/80 x Y =1/3

                                 1/5         x  Y=1/3

                                                     Y= 1/3:1/5

                                                     Y =1/3x 5/1

                                                     Y = 5/3