[tex]5(x^4+x^2)=(2x^2+x)^2 \\ 5x^2(x^2+1) = 4x^4+4x^3+x^2 \\ 5x^2(x^2+1) = x^2(4x^2+4x+1) \\ 5x^2(x^2+1)-x^2(4x^2+4x+1) = 0 \\ x^2\Big(5(x^2+1)-(4x^2+4x+1)\Big) = 0 \\ x^2(5x^2+5-4x^2-4x-1) = 0 \\ x^2(x^2-4x+4) = 0 \\ x^2(x-2)^2 = 0 \\ \\ \boxed{1} \quad x^2 = 0 \Rightarrow x= 0 \\ \\ \boxed{2} \quad (x-2)^2=0 \Rightarrow x = 2 \\ \\ \Rightarrow x\in\Big\{0,2\Big\} \Rightarrow$ Numarul elementelor multimii este 2.[/tex]
