1)
[tex]49-14y+y^2=y^2-14y+49\\\Delta=(14)^2-4*1*49\\\Delta=196-194\\\Delta=0\\y_1=\frac{14}2=7\\49-14y+y^2=(y-7)^2[/tex]
2)
[tex]m^2+n^2-2mn=m^2-2mn+n^2=(m-n)^2[/tex]
3)
[tex]4x^2-64y^2=(2x-8y)(2x+8y)[/tex]
4)
[tex](x-3)^2-9x^2=x^2-6x+9-9x^2=-8x^2-6x+9\\\Delta=(-6)^2-4*(-8)*9\\\Delta=36+288\\\sqrt{\Delta}=18\\x_1=\frac{6-18}{-16}=\frac{-12}{-16}=\frac34\\x_2=\frac{6+18}{-16}=\frac{24}{-16}=-\frac{6}4=-\frac32\\(x-3)^2-9x^2=-8(x-\frac34)(x+\frac32)[/tex]
