Question

ex 5 dau corona....

Answer 1

2x+1=D14={1,2,7,14}, unde x∈N
2x+1=1⇔2x=0⇔x=0∈N
2x+1=2⇔2x=1⇔x=1/2∉N
2x+1=7⇔2x=6⇔x=3∈N
2x+1=14⇔2x=13⇔x=13/2∉N

x∈{0,3}