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Daca x+y= -√2 ai xy= - 12.
Calculati :
a)x²+y²
b)x-y


Răspuns :

x+y=-√2
xy=-12

formula de calcul prescurtat:
(x+y)²=x²+2xy+y²

a) →x²+y²=(x+y)²-2xy
x²+y²=(-√2)² -2* (-12)= 2+ 24=26

b) formula de calcul prescurtat:
(x-y)²=x²-2xy+y²=x²+y²-2xy=26-2*(-12)=26+24=50

√(x-y)²=x-y
→x-y=√50=5√2