=>(x+42000+1) + (x+32001+1) = (x+22002+1) + (x+12003+1)
=>(x+4+20002000) + (x+3+20012001) - (x+2+20022002) - (x+1+20032003) = 0
=>(x+20042000)+(x+20042001) - (x+20042002) - (x+20042003) = 0
=>(x+2004) (12000+12001−12002−12003) =0
=>Vì (12000+12001−12002−12003) >0
=>x+2004 = 0 => x= −2004