$2x(x-7)-(x-1)^2=x^2+7$
$<=>2x^2-14x-x^2+2x-1=x^2+7$
$<=>x^2-12x-1=x^2+7$
$<=>-12x-1=7$
$<=>x=-2/3$
$(x+1)^2+(x-3)^2=2(x-2)(x-4)+15x+1$
$<=>x^2+2x+1+x^2-6x+9=2x^2-8x-4x+16+15x+1$
$<=>2x^2-4x+10=2x^2+3x+17$
$<=>-4x+10=3x+17$
$<=>x=-1$
$ x(x+3)^2-3x=(x+2)^3+1$
$<=>x^3+6x^2+6x=x^3+4x^2+4x+2x^2+8x+8+1$
$<=>6x^2+6x=6x^2+12x+9$
$<=> -6x=9$
$<=>x=-3/2$
Vậy ........