Câu hỏi của Duy Khánh

Question

Tìm X
( 2/11x13 + 2/13x15+...+ 2/19x21)x462-( 204: (x-105):12=19
chú ý: / là phân số
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Đỗ Thảo Nguyên · Accepted Answer

(11×132​+13×152​+15×172​+17×192​+19×212​)×462−y=19

⇒(111−113+113−115+115−117+117−119+119−121)×462−�=19⇒(111​−131​+131​−151​+151​−171​+171​−191​+191​−211​)×462−y=19

⇒(111−121)×462−�=19⇒10231×462−�=19⇒(111​−211​)×462−y=19⇒23110​×462−y=19

⇒20−�=19⇒�=20−19=1⇒20−y=19⇒y=20−19=1Câu trả lời: (11×132​+13×152​+15×172​+17×192​+19×212​)×462−y=19

⇒(111−113+113−115+115−117+117−119+119−121)×462−�=19⇒(111​−131​+131​−151​+151​−171​+171​−191​+191​−211​)×462−y=19

⇒(111−121)×462−�=19⇒10231×462−�=19⇒(111​−211​)×462−y=19⇒23110​×462−y=19

⇒20−�=19⇒�=20−19=1⇒20−y=19⇒y=20−19=1

Nguyễn Thị Thương Hoài · Answer

Tìm $x$ biết:

($\dfrac{2}{11\times13}$ + $\dfrac{2}{13\times15}$+...+ $\dfrac{2}{19\times21}$) x 462 - (204: ($x-105$):12) =19

($\dfrac{1}{11}-\dfrac{1}{13}$+ $\dfrac{1}{13}$ - $\dfrac{1}{15}$+...+ $\dfrac{1}{19}$ - $\dfrac{1}{21}$) x 462 - (204 : ($x$ -105):12) =19

($\dfrac{1}{11}$ - $\dfrac{1}{21}$) x 462 -  $\dfrac{204:(x-105)}{12}$ = 19

$\dfrac{10}{213}$ x 462 - $\dfrac{204:\left(x-105\right)}{12}$ = 19

20 - $\dfrac{204:\left(x-105\right)}{12}$ = 19

204:($x$ - 105):12 = 20 - 19

204:($x-105$):12 = 1

204: ($x$ - 105) = 12

$x-105$ = 204: 12

$x$ - 105 = 17

$x$          = 17 + 105

$x$         = 122Câu trả lời: Tìm $x$ biết: