High scores, help me choose one of these

If I choose, the first choice is Dell,Because I've also seen these two machines,Although it's 1000 yuan worse than Lenovo's,But its performance is definitely better than Lenovo's machine,Many friends are in line with the fact that it's enough to buy this now,In fact, it's good to spend 1000 more to buy a much better performance book,Dell's first of all, the graphics card is better,Secondly, its hard disk and optical drive are now engaged in online **,Can be added to 120 and ***rw,There will definitely be more discounts in the future, And Dell can now add 700 to the door maintenance for three years, if I were you, I would definitely choose Dell to rush these three years of service. Two of my roommates bought Dell, and many other dormitories bought them, none of them were broken, unlike many people who say that the heat is easy to crash. Hope it works for you, hehe.

The first one, Lenovo's price point is moderate, and I only follow the principle of sufficiency.

8400 is flashy, I don't think it's necessary to pay an extra 1000 yuan to buy a good processor. HP can also be selected, but the AMD processor is slightly worse, and the graphics card is also poor, so choose Lenovo, which is waiting.

If you use a general application, all laptops are basically the same, but if you want to play games, you have to look at the graphics card! So the second one is the best choice for you, a discrete 8400M graphics card, which is enough to handle almost all games! Hello, what is there to consider!

Of course, the notebook is IBM's good, but ** high, the Japanese and Korean notebooks have a good appearance, the function is not good, not as good as the American ones, such as IBM, dell's, dell is very famous abroad, but in China, and in Asia, it is still Lenovo's first sales volume, so it is better to buy Lenovo's 420at, but Lenovo also has a book with Celeron processor, it seems to be 410, before the price is adjusted, 3999 can be bought, but it is a set of displays, enough to learn, if you want to play games, The rest of the money is good to buy a PSP.

If it were me, the third one I wouldn't have thought about, who uses linux for the operating system?

Buy Lenovo's, after-sales service is better.

The second one is good, but too expensive.

So let's buy the first one, the first sex price is already very high.

The third one doesn't have to be considered.

If you use the third one on a daily basis, it will suffice.

The game is the first one.

If you are a game enthusiast, it is recommended to buy 2 land.

The second game is the second.

dell, Lenovo graphics card is low, and it's a bit difficult to play WOW.

The first one is good, and there is Lenovo's new 410

It depends on your purpose requirements.,If you want to play the game, you should choose a high match.。

The most cost-effective: Lenovo Sunburst 420AT2080

Look at the picture

Doing math problems and drawing lots of pictures will make it easier for you to understand.

The detailed steps are written down on paper.

Let f(x)=y

In order to satisfy Roll's median value theorem, three prerequisites need to be satisfied: , f(x) is continuous on [-1,1]; , f(x) is derivable in (-1,1); ③、f(-1)=f(1)。Each of the four options can be compared with the above 3 prerequisites.

Option A satisfies the condition, the derivative does not exist at x=0, and the condition is not satisfied.

Option b satisfies the condition, is not derivative at x=0, and does not meet the condition.

Option C satisfies 3 conditions.

Option d satisfies the condition , f(-1) ≠ f(1), and does not meet the condition.

Only C is correct, choose C.