Tìm x a) x – 7/ 36 = -4/ 7-x b) 0,2/ |2x-1|- 20/11.13 – 20/13.15 – 20/ 15.17-….-20/53.55=3/11

Đáp án:

`a)`

`(x-7)/36 = -4/(7-x)`

`to (x-7)/36 = 4/(x-7)`

`to (x-7)^2=144`

`to` \(\left[ \begin{array}{l}x-7=12\\x-7=-12\end{array} \right.\) `to` \(\left[ \begin{array}{l}x=19\\x=-5\end{array} \right.\) 

Vậy `x in {-5;19}`

`b)`

`(0,2)/ |2x-1|- 20/11.13 – 20/13.15 – 20/ 15.17-….-20/53.55=3/11`

`to (0,2)/|2x-1| – 10.(2/11.13+2/13.15+2/15.17+…+2/53.55)=3/11`

`to (0,2)/|2x-1| – 10.(1/11-1/13+1/13-1/15+1/15-1/17+…+1/53-1/55)=3/11`

`to (0,2)/|2x-1| – 10.(1/11-1/55)=3/11`

`to (0,2)/|2x-1| – 10. 4/55=3/11`

`to (0,2)/|2x-1| – 8/11 = 3/11`

`to (0,2)/|2x-1| = 1`

`to |2x-1|=0,2`

`to |2x-1|=1/5`

`to` \(\left[ \begin{array}{l}2x-1=\dfrac{1}{5}\\2x-1=-\dfrac{1}{5}\end{array} \right.\) `to` \(\left[ \begin{array}{l}2x=\dfrac{6}{5}\\2x=\dfrac{4}{5}\end{array} \right.\) `to` \(\left[ \begin{array}{l}x=\dfrac{3}{5}\\x=\dfrac{2}{5}\end{array} \right.\) 

Vậy `x in {3/5;2/5}`