1) 69-(13-y)^2=-y
69-(169-26y+y^2)=-y
69-169+26y-y^2-y=0
-y2+25y-100=0 /×(-1)
y^2-25y+100=0
D=625-400=225=15^2
y1=25+15/2=20
y2=25-15/2=5
а) 16