x^2+10x+26= x^2+10x +25-25+26=(х+5) ^2 + 1
x^2-5x-1 = x^2-5x +6,25-6,25-1=(х-2,5) ^2 -7,25
x^2+10x+26=((x)^2+(2*x*5)+5^2)-5^2+26=(x+5)^2+1;
x^2-5x-1=((x)^2-(2*x*2,5)+(2,5)^2)-(2,5)^2-1=(x-2,5)^2-7,25
