原式=(4(x+2)(x-2)+x-2(x+2)(x-2))÷1x-2
=x+2(x+2)(x-2)•(x-2)
=1．
It is a strange phenomenon that some young people today think it is their parents’responsibility to earn money and_______ to spend it.
A．them
B．they
C．their
D．theirs
两个氘核结合成一个氦核的过程中可释放多少核能？若1千克氘完全结合成氦，则可放出多少能量？已知m氘＝2.0141u，m氦＝4.0026u．阿伏伽德罗常数N0＝6×1023.1/mol．
