It takes ____ one hour ____ his homework.

— Bob, can you read the number 2,357,018?

— Yes, I can. It's

已知函数f（x）=log₃（ax+b）的图象经过点A（2，1）、B（5，2），

（1）求函数f（x）的解析式及定义域；

（2）求$f\left(14\right)÷f\left(\frac{\sqrt{3}+1}{2}\right)$的值．

    We live in the Internet age when much business is conducted online. How shall we mark the special occasions？____There are numerous websites available online that specialize in electronic cards，or e­cards in short.

    ____Cards have been a popular way to express one's feelings and gratitude. Earlier，there were traditional cards handpicked for special occasions but now，those are being replaced by e­cards. E­cards are friendly in the world，which means you can send them to anyone around the world，to your friends，relatives，family，cousins，children，colleagues and numerous others.____There are Thank You Cards，Birthday Cards，Invitation Cards，Romantic Cards，Seasonal Cards Congratulation Cards，and Cards For Special Events. In other words，you have cards for any occasion. Many sites offer the cards free.____Almost all the e­cards are available online for print. If you have an office party and want to make it exceptional，printable Invitation Cards are not difficult to find. You can also give them printable Thank You Cards and then Congratulation Cards to honor the best colleagues for their contributions and efforts._ ____ Just register with an online e­card website，look through the different kinds of cards，select your cards，download and print the cards you like. You get everything，basically nothing spent at your side.

    With e­cards，send your messages and best wishes to any person around the globe.

A．Why do we send cards anyway?

B．E­cards are in fashion these days.

C．What types of cards are there?

D．Where can we find the suitable cards we like?

E．Therefore，what do you need to do to print e­cards?

F．E­cards are more convenient than traditional cards.

G．In addition，you also have printable e­cards and those are free too.

小明学习了热学的有关知识后，知道水的比热是4.2×10³焦/（千克•℃），他想估算一下自己家每天烧水、做饭需要的热量，于是小明仔细记录了他家每天烧水、煮饭、炒菜需要的时间，并把它折算成烧水时间，相当于每天将30千克20℃的水烧开．

（1）小明家每天烧水做饭需要多少热量？

（2）如果普通煤的燃烧值为3×10⁷焦/千克，从理论上讲小明家每天烧水做饭需要多少千克煤？

（3）小明家实际平均每天需要烧4块蜂窝煤，按每块蜂窝煤含煤0.5千克算，他家每天实际用煤2千克，由此小明计算出他家煤炉的效率只有16.5%，你认为小明家煤炉效率低的原因是什么？

（4）从大的方面讲，家用煤炉除了热效率低浪费能源的缺点外，另一个主要缺点是什么？