x,y互为相反数,则x+y=0.
a,b互为倒数,则ab=1.
则(x+y)-4ab=-4.
No one could recognize me after I got my new transistors in the 31 (1960).There were times when my size was 32 (total) changed. I became small and thin but I got cleverer and cleverer, quicker and quicker. And my memory became so large 33 I couldn’t believe it! But I was always so lonely 34 (stand) there by myself, 35 in the early 1960s, they gave me a family 36 (connect) by a network. I could share information 37 others and we could talk to each other. At about the same time we learned to talk to humans using BASIC. I was brought into people’s homes in the 1970s. Since then, my family and I 38 (use) by 39 (billion) of people to deal with information and communicate with each other around the world by the Internet. I love 40 (use) to connect people who aren’t close enough to speak to each other. I have truly been built to serve the human race since my birth.
用高压锅煮饭,熄火后用冷水将锅冷却,拿去限压阀后打开锅盖,可以看到锅内的粥仍在沸腾,而普通的铝锅却看不到这种现象。这是因为:
A.熄火后,锅内的温度迅速降到100%:以下,但由于打开锅盖后气压降低,所以粥会重新沸腾
B.粥的流动性差,不易降温,熄火后即使不浇冷水,不拿去限压阀,粥也要沸腾较长时间
C.熄火后,锅内的温度仍然高于100℃,即使不冷却,不拿去限压阀,粥也会在沸腾
D.熄火后,锅内的温度仍然高于100℃,冷却后锅内气压比原来降低,所以粥会重新沸腾