若（x＋4）(x－3) = x2 + x+n,则 n=
-12
（x＋4）(x－3) = x2 + x-12，故n=-12.
Studies show that people are more __________ to suffer from back problems if they always sit before computer screens for long hours.
A．likely
B．possible
C．probable
D．sure
只读存储器(ROM)内所存的数据是固定不变的。
A．正确
B．错误
