1)x2+6x+8=0
2)x2-5+6=0
3)x2-2x-15=0
4)x2+6x-40=0
5)x2+x-2=0

1.D=36-4*8=36-32=4.х1=-6-4/2=-5х2=-6+4/2=-12.D=25-4*(-6)=25+24=49.х1=5-7/2=-1х2=5+7/2=63.D=4-4*(-15)=4+60=64.х1=2-8/2=-3х2=2+8/2=54.D=36-4*(-40)=36+160=196.х1=6-14/2=-4х2=6+14/2=105.D=1-4*(-2)=1+8=9.х1=-1-9/2=-5х2=-1+9/2=4