Đáp án `+`Giải thích các bước giải:
` a , ` Ta thấy `:`
` |x + 1/(1.2)| ` $\geq$ `0`
` | x + 1/(2.3)| ` $\geq$ `0`
......
` | x + 1/(99 . 100)| ` $\geq$ `0`
` -> |x+1/(1.2)| + |x+1/(2.3)| + .... + |x+1/(99.100)| ` $\geq$ `0`
`-> 100x ` $\geq$ `0`
`-> x ` $\geq$ `0`
` => x+ 1/(1.2) + x + 1/(2.3) +....... +( x +1/(99.100) = 100x `
`-> (x+x+x+......+x) + (1/(1.2) + 1/(2.3)+......+1/999.100)) = 100x`
`-> 99x + (1-1/2+1/2-1/3+....+1/99-1/100)=100x `
`-> 99x + (1-1/100) = 100x `
`-> 99x + 99/100 = 100x `
` -> 99/100 = 100x - 99x `
`-> 99/100 = x `
` b) ` Ta thấy:
` | x + 11/17| ` $\geq$ `0`
` | x + 2/17|` $\geq$ `0`
` | x + 4/17| ` $\geq$ `0`
`-> |x+11/17| + |x+ 2/17| + | x + 4/17| ` $\geq$ `0`
` -> 4x ` $\geq$ `0`
`-> x `$\geq$ `0`
` => x+11/17 + x + 2/17 + x + 4/17 = 4x `
`-> (x+x+x) + (11/17+4/17+2/17) =4x`
`-> 3x + 1 = 4x`
`-> 1 = 4x - 3x = x ` `
` c ) ` Ta thấy :
` |x+0,8| ` $\geq$ `0`
` |x+5,2| `$\geq$ `0`
` |x + 9,7| `$\geq$ `0`
` -> |x+0,8| + |x + 5,2| + |x + 9,7| ` $\geq$ `0`
`-> 4x `$\geq$ `0`
`-> x ` $\geq$ `0`
`=> x + 0,8 + x + 5,2 + x + 9,7 = 4x`
`-> (x+x+x) +(0,8+5,2+9,7)=4x`
`-> 3x + 15,7 = 4x`
`-> 15,7 = 4x-3x=x `
