{ x2 - [ 82 - ( 52 - 8 . 3 )3 -7 . 9 ]3 - 4 . 12 }3 = 1
=>{x2-[82-(25-24)3-7.9]3-4.12}3=1
=>[x2-(82-13-7.9)3-4.12]3=1
=>[x2-(64-1-63)3-4.12]3=1
=>(x2-03-4.12)3=1
=>(x2-0-48)3=1
=>(x2-48)3=1
=>(x2-48)3=13
=>x2-48=1
=>x2=1+48
=>x2=49
=>x2=72 hoặc x2=(-7)2
=>x=7 hoặc x=-7