Đáp án:
`x=-1`
Giải thích các bước giải:
Ta có:
`\qquad 5/{21.38}+5/{23.42}+5/{23.50}+5/{27.50}+x={-503}/{513}`
`=>5/{21.19.2}+5/{23.21.2}+5/{23.25.2}+5/{27.25.2}+x={-503}/{513}`
`=>5/ 4 .(2/{19.21}+2/{21.23}+2/{23.25}+2/{25.27})+x={-503}/{513}`
`=>5/ 4 . (1/{19}-1/{21}+1/{21}-1/{23}+1/{23}-1/{25}+1/{25}-1/{27})+x={-503}/{513}`
`=>{53}/{513}+5/ 4. (1/{19}-1/{27})+x={-503}/{513}`
`=>{503}/{513}+5/ 4 . 8/{513}+x=0`
`=>{503}/{513}+{10}/{513}+x=0`
`=>1+x=0`
`=>x=-1`
Vậy `x=-1`
