Đáp án: `x = 1/3`
Lời giải
`x.(2/(1.2) + 2/(2.3) + 2/(3.4) + ... + 2/(99.100))=33/50`
`⇒x.2(1/(1.2) + 1/(2.3) + 1/(3.4) + ...+ 1 /(99.100))=33/50`
`⇒x.2(1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 +...+ 1.99 - 1/100) = 33/50`
`⇒x.2(1/1 - 1/100) = 33/50`
$⇒$ `x .2.99/100 = 33/50`
`⇒x . 99/50 = 33/50`
`⇒x = 33/50 : 99/50`
`⇒x = 33/50 . 50/99`
`⇒x = 1/3`
Vậy `x = 1/3`
