Question

Se dau numerele reale x,y cu propietatea ca x^2+4y^2=52 si x-2y=10. Calculati valorile expresiilor xy,x+2y !! Va rog muult !!

Answer 1

(x-2y)^2 =100= x^2-4xy+4y^2=52-4xy
52-4xy=100
4xy= 52-100
xy = - 12

(x+2y)^2 = x^2+4xy+4y^2 = 52-48=4
lx+2yl=2
x+2y=2
x+2y=-2