(x-5)(x+3)=-15x^2-2x-15=-15x^2-2x=0x(x-2)=0x=0或x=2(x-1)(x+2)=1x^2+x-2=1x^2+x-3=0x^2+x+1/4-1/4-3=0(x+1/2)^2-13/4=0(x+1/2-√13/2)(x+1/2+√13/2)=0x=-1/2+√13/2或x=-1/2-√13/2