(х-7)(х+7)+(х-2)^2=11х+30-(х-5)^2 решите,

x^2 - 49 + x^2 - 4x + 4 = 11x + 30 - (x^2 - 10x + 25)
2x^2 - 4x - 45 = - x^2 + 21x + 5 
2x^2 - 4x - 45 + x^2 - 21x - 5 = 0 
3x^2 - 25x - 50 = 0 
D = 625 + 600 = 1225 = 35^2
x1 = ( 25 + 35)/6 = 10;
x2 = ( 25 - 35)/6 = - 5/3;