chiu thoi

\(\left(\frac{2}{11\times13}+\frac{2}{13\times15}+\frac{2}{15\times17}+\frac{2}{17\times19}+\frac{2}{19\times21}\right)\times462-x=19\)

\(\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{19}-\frac{1}{21}\right)\times462-x=19\)

\(\left(\frac{1}{11}-\frac{1}{21}\right)\times462-x=19\)

\(\frac{10}{231}\times462-x=19\)

\(20-x=19\)

\(\Rightarrow x=20-19=1\)

1+1= ????????????????? đố ai giải được 

\(\Leftrightarrow\left(\dfrac{1}{11}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{15}+...+\dfrac{1}{19}-\dfrac{1}{21}\right)\cdot462-y=19\)

\(\Leftrightarrow20-y=19\)

hay y=1

y= 100% luôn 

Tìm x

3(1-x)=-4x-2

= 100% luôn

no          

                                                                                                                                                                                          biet

minh nghi y = 1 

dung thi t nhe !

y= 10000000000000000000000000000000000000000000................% luôn nếu két quả này sai thì mình chịu

bai nay ko kho

thì bạn thử giải đi

nó không biết làm đâu