[tex]a)x^2-3x+2=0\\\\a=1\\b=-3\\c=2\\\\x=\frac{-(-3)+-\sqrt{(-3)^2-4.1.2} }{2.1}\\\\x=\frac{3+-\sqrt{9-8} }{2}\\\\x=\frac{3+-\sqrt{1^2} }{2}\\\\x=\frac{3+-1}{2} \\\\x^l=\frac{3+1}{2} =\frac{4}{2} = 2\\\\x^l^l=\frac{3-1}{2} =\frac{2}{2}=1 \\\\S={1,2} = IV[/tex]

[tex]b) y^2-7y+12=0\\a=1\\b=-7\\c=12\\\\y=\frac{-(-7)+-\sqrt{(-7)^2-4.1.12} }{2}\\\\y=\frac{7+-\sqrt{49-48} }{2}\\\\y=\frac{7+-\sqrt{1^2} }{2}\\\\y=\frac{7+-1}{2} \\\\y^l=\frac{7+1}{2} =\frac{8}{2} = 4\\\\y^l^l=\frac{7-1}{2} =\frac{6}{2} =3\\\\S=3,4 = II[/tex]

[tex]c) x^2-5x-6=0\\a=1\\b=-5\\c=-6\\\\x=\frac{-(-5)+-\sqrt{(-5)^2-4.1.-6} }{2}\\\\x=\frac{5+-\sqrt{25+24} }{2}\\\\x=\frac{5+-\sqrt{49} }{2}\\\\x=\frac{5+-7 }{2}\\\\x^l=\frac{5+7}{2} =\frac{12}{2} =6\\\\x^l^l=\frac{5-7}{2} =\frac{-2}{2} =-1\\\\S=-1,6[/tex]

[tex]d)t^2+6t+8=0\\a=1\\b=6\\c=8\\\\t=\frac{-6+-\sqrt{6^2-4.1.8} }{2}\\\\t=\frac{-6+-\sqrt{36-32} }{2}\\\\t=\frac{-6+-\sqrt{4} }{2}\\\\t=\frac{-6+-2}{2} \\\\t^l=\frac{-6+2}{2} =\frac{-4}{2} = -2\\\\t^l^l=\frac{-6-2}{2} =\frac{-8}{2} = -4\\\\S=-4,-2[/tex]