Question

как решить х+у=12
ху=35

Answer 1

{х+у=12
{ху=35
=
{х=12-у
{(12-у)у=35
=
{12у-у^2=35
{-у^2+12-35=0
-у^2+12у-35=0 /*(-1)
у^2-12у+35=0
D=144-4*35=4
D=2
у1=12+2:2=7; ×1=12-7=5
у2=12-2:2=5; ×2=12-5=7