At the meeting, they discussed three difficult _______ to the study of mathematics.
A:approaches
B:accesses
C:means
D:methods
—Where is Jiangxi?
—It's _____ the south ____China. ( )
①N2(g)+O2(g)⇌2NO(g)△H1=a kJ•mol﹣1
②2NO(g)+O2(g)⇌2NO2(g)△H2=b kJ•mol﹣1
③CO(g)+ 12 O2(g)⇌CO2(g)△H3=c kJ•mol﹣1
④2CO(g)+2NO(g)⇌N2(g)+2CO2(g)△H4
请回答下列问题:
若关于x的一元二次方程kx2-2x-1=0有两个不相等的实数根,则k的取值范围是( )