Răspuns:
Explicație pas cu pas:
1) fractie supraunitara, daca numarator > numitor, deci x-2>6, ⇒x>6+2, ⇒x>8 si x∈N.
2) fractie echiunitara, daca numarator = numitor, deci 17=2x+1, ⇒2x=17-1, ⇒2x=16, ⇒x=16:2=8.
3) [tex]\frac{2x+1}{21}=\frac{3}{7},~deci~(2x+1)*7=21*3,~2x+1=\frac{21*3}{7},~2x+1=9,~2x=9-1,~2x=8,~x=8:2=4.\\[/tex]
4) fractie subunitara, daca numarator < numitor, deci 2x²-3<31, ⇒2x²<31+3, ⇒2x²<34 |:2, ⇒x²<17, ⇒√(x²)<√17, ⇒|x|<√17
Deoarece x este natural, ⇒x∈{-4,-3,-2,-1,0,1,2,3,4}