(x+2)²+(x-1)²-2(x+3)(x-3)=28
x^2+4x+4+x^2-2x+1-2(x^2-9)=28
x^2+4x+4+x^2-2x+1-2x^2+18=28
2x=28-23
2x=5
x=5/2