Đáp án:
`x\in{10;-11}`
Giải thích các bước giải:
`x.(x+1)=110`
`=>x.x+x.1=110`
`=>x.x+x=110`
`=>x.x+x-110=0`
`=>x.x+(11-10)x-110=0`
`=>x.x+11x-10x-110=0`
`=>(x.x+11x)-(10x+110)=0`
`=>x.(x+11)-(10x+11.10)=0`
`=>x.(x+11)-10.(x+11)=0`
`=>(x-10)(x+11)=0`
`=>[(x-10=0),(x+11=0):}`
`=>[(x=0+10),(x=0-11):}`
`=>[(x=10),(x=-11):}`
Vậy `x\in{10;-11}`