2.

[tex](x+3)(x-8)=0\\x^2+3x-8x-24=0\\x^2-5x-24=0[/tex]

3.

[tex]x^2-x = 2x+4\\x^2-x-2x-4=0\\x^2-3x-4=0\\x1 = \frac{3+\sqrt{9+16}}{2} = 4\\x2 = \frac{3-\sqrt{9+16}}{2} = -1\\[/tex]