Question

Rezolvati in IR ecuatia bipatrata: $x^{4} +11 x^{2} +18=0$

Answer 1

x e R  

daca x < 0 => x^2 > 0 si x^4 >0 => x^4 +11*x^2 >0
=> x^4 +11*x^2 +18>18
daca x>0 => acelasi lucru ca la x<0
daca x=0 =>  0+0+18 =18

=> x^4 +11*x^2 +18 =0 nu are solutii in R