(3x+3)^2=x^2+(x+1)^2+(x+2)^2+2644

Question

(3x+3)^2=x^2+(x+1)^2+(x+2)^2+2644

Answer 1

9x^2 + 18x + 9 = x^2 + x^2 + 2x + 1 + x^2 + 4x + 4 + 2644
9x^2 + 18x + 9 = 3x^2 + 6x + 2649
9x^2 + 18x + 9 - 3x^2 - 6x - 2649 = 0 
6x^2 + 12x - 2640 = 0  //: 6
x^2 + 2x - 440 = 0 
D = 1 + 440 = 441 = 21^2
x1 = - 1 + 21 = 20;
x2 = - 1 - 21 = - 22