Question

Determinati valoare expresiei :

a) $x^{2} - y^{2}$ , stiind ca x-y=4 si x+y=6
b) x+y , stiind ca $x^{2} - y^{2} = 14 ,si , x-y=7$

Answer 1

X²-Y²=X²-Y²+X*Y-X*Y=X*(X-Y)+Y*(X-Y)=(X+Y)*(X-Y)=6*4=24

X²-Y²=(X+Y)*(X-Y)
14=(X+Y)*7
X+Y=14:7=2