Question

вынесение общего множителя: y(7-y)-(y-7)=0

Answer 1

y(7-y)+1(7-y)=(y+1)(7-y)

Answer 2

7y-y2-y+7=0
-y2+6y+7=0
D=36-4*(-1)*7=36+28=64
x1=(-6-8)/-2=7
x2=(-6+8)/-2=-1