{xy=5
{xy²-x²y=80
{xy=5
{xy(y-x)=80
5(x-y)=80|÷5
x-y=16
y=(x-16)
xy=5
x×(x-16)=5
x²-16x-5=0
D=(-(-16))²-4×1×(-5)=256+20=276
x1=(-(-16)-√276)/2×1=(16-16,61)/2=(-0,61)/2=-0,305
x2=(-(-16)+√276)/2×1=(16+16,61)/2=36,61/2=16,305
y1=(x1-16)
y1=-0,305-16
y1=-16,305
y2=(x2-16)
y2=16,305-16
y2=0,305
(-0,305;-16,305); (16,305;0,305).
Проверка:
х1×у1=5
(-0,305)×(-16,305)=5
4,973=5
5=5-истина.
х2×у2=5
16,305×0,305=5
4,973=5
5=5-истина
х1-у1=16
-0,305-(-16,305)=16
-0,305+16,305=16
16=16-истина.
х2-у2=16
16,305-0,305=16
16=16--истина.