Найдите значение выражения(7-а)(7+а)-а(25-а) при а=-21/25(это дробь если что)​

I want to touch upon the problem of modern technologies. To my mind, people can’t live without them. TV, telephones, radio, the Internet, e-books, and many other devices are very useful and important things in our life.

So, firstly, modern technologies give us much information about the world. Sitting at home we can learn all news and all details about any event. The use of modern technologies is one of the best ways to explore the world.

Secondly, thanks to modern technologies we can communicate with people, to write letters, to find new friends. It is a real pleasure. When you miss your family, you can call and see the people who are dear to you using Skype.

Thirdly, with the help of modern technologies we can gain different knowledge. We can study various subjects. We can learn everything. It simplifies our life. Modern technologies have a lot of pros, but they have some cons too. You should mind that they may damage your health. But, to my mind, they still have more pros than cons.

Thanks to the Internet you can do almost everything. You can watch movies, play games, make various projects, buy many things, read books, and do many others.

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Complete the sentences with a verb in the negative.
1.We had English yesterday buy we didn't have chemistry.
2.I saw joe this morning But I didn’t see Ben
3.Jack came last week but he didn’t come yesterday
4.Sally worked on Saturday but she didn’t work on Sunday
5.The Kellys went to Spain but they  didn’t go to Madrid.
6.The liked the bech but they  didn’t like the campsite.
7.I enjoyed the book but I didn’t enjoy the film.
8.Sadie took her anorak buy she  didn’t take an umbrella.
9.The hotel manager spoke English but he didn’t speak Italian.
10.We ate the chips but we didn’t eat  the salad.

1. Did Alexander bell invent the telephone? Yes, he did
2. Was Clare a wan film star? – No, she didn’t.
3. Did the Romans live in England? – No, they didn’t.
4. Did Paul McCarney write the song Angels? – Yes, he did
5. Did Matt and Jack go to France on holiday? – No, they didn’t.
6. Did they have a good time? – Yes, they did.
7. Did Billy shoot the sheriff? – No, he didn’t.
8. Did you enjoy doing the exercise? -  Yes, I did.