a)
[tex] {x}^{2} - 7 = 0[/tex]
[tex] {x}^{2} = 7[/tex]
[tex]x = + - \sqrt{7} [/tex]
[tex] x_{1} = - \sqrt{7} \\ x _{2} = + \sqrt{7} [/tex]
b)
[tex] {x}^{2} - 5x = 0[/tex]
[tex]x \times (x - 5) = 0[/tex]
[tex]x = 0 \\ x - 5 = 0[/tex]
[tex] x_{1} = 0 \\ x_{2} = 5[/tex]
