a)
[tex](x - 2 {)}^{2} = 0[/tex]
[tex]x - 2 = 0[/tex]
[tex]x = 2[/tex]
b)
[tex]( - 4 {)}^{2} - 4 \times 1 \times 7[/tex]
[tex] - 12[/tex]
c)
[tex] {6}^{2} - 4 \times 1 \times ( - 2)[/tex]
[tex]44[/tex]
d)
[tex] {6}^{2} - 4 \times 1 \times ( - 3)[/tex]
[tex]48[/tex]
