Răspuns:
a) 2x-x²>= 0
2x-x²=0
x(2-x)=0
x=0
x=2
x apartine intervalului [0;2]
b) 1-x >=0
x<= 1
x apartine (-infinit ; 1]
c)
[tex] \frac{x}{x ^{2} + 4} \geqslant 0 \\ \\ x \geqslant 0 \\ \\ {x}^{2} + 4 \geqslant 0 \\ \\ x \: apartine \: [/tex]
[2;infinit)