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x+y=4 si x^2+y^2=12 . Calculati x-y

Răspuns :

x+y=4
x²+y²=12

x²+2xy+y²=16
x²+y²=12

2xy+12=16
2xy=4
xy=2
x=2/y
2/y+y=4
2+y²=4y
y²-4y+2=0
y₁=2-√2      x₁=4-y=4-2+√2=2+√2
y₂=2+√2      x₂=4-y=4-2-√2=2-√2
x₁-y₁=2+√2-(2-√2)=2+√2-2+√2=2√2
x₂-y₂=2-√2-(2+√2)=2-√2-2-√2=-2√2