помогите решить
(x+13)^2=x^2+(x+4)^2+x^2+81

(x+13)² =x²+x²+8x+16+x²+81x²+26x+169 =3x²+8x+97x² -3x²+26x -8x+169 -97 =0-2x² +18x +72 =0, :(-2)x² -9x -36 =0D =81 +144 =225 =15²x1 =(9 -15)/2 = -3x2 =(9 +15)/2 =12ответ: x= -3, x =12