1  а) x^2-6x-7=0

x1+x2=6  

x1*x2=-7

x1=7

x2=-1

б) x^2+6x+5=0

x1+x2=-6

x1*x2=5

x1=-5

x2=-1

в) x^2+12x+27=0

x1+x2=-12

x1*x2=27

x1=-9

x2=-3

2 x^2+px-8=0

x1+2=-p

x1*2=-8

x1=-8/2=-4

x1+2=-p

-4+2=-p

-p=-2

p=2

3 (x+7)(x-2)=0

x^2+7x-2x-14=0

x^2+5x-14=0