1) 
2)
x_1=2; x_2=-3;" alt="(x-2)(2x+6)=0 => x_1=2; x_2=-3;" align="absmiddle" class="latex-formula">
3)
x(x^2-9)=x(x-3)(x+3) " alt=" x^3-9x=0 => x(x^2-9)=x(x-3)(x+3) " align="absmiddle" class="latex-formula">
x_1=0; x_2=3; x_3=-3" alt="=> x_1=0; x_2=3; x_3=-3" align="absmiddle" class="latex-formula">
4) 