Ta có: (x+3)4(x+3)4 +(4−2x)4(4−2x)4 =(1−3x)4(1−3x)4
⇔(x+3)4(x+3)4 - (1−3x)4(1−3x)4 +(4−2x)4(4−2x)4=0
⇔[(x+3)2(x+3)2 - (1−3x)2(1−3x)2][(x+3)2(x+3)2 + (1−3x)2(1−3x)2]+(4−2x)4(4−2x)4=0
⇔(4x+2)(4-2x)[(x+3)2(x+3)2 + (1−3x)2(1−3x)2]+(4−2x)4(4−2x)4=0
⇔(4-2x){(4x+2)+[(x+3)2(x+3)2 + (1−3x)2(1−3x)2]+(4−2x)3(4−2x)3}=0
⇔ x=2 hoặc (4x+2)+[(x+3)2(x+3)2 + (1−3x)2(1−3x)2]+(4−2x)3(4−2x)3=0 (1)
