упростите выражение. a2-14a+49,a=407

Привести химические формулы следующих соединений:кремнезем,пищевая сода

 ПОМОГИТЕ ПОЖАЛУЙСТА

Выбрать правильное и составить 7 вопросов в Present Simple

1) I (am/is) a student

2) I (study/studies medecine at the uneversity in my town

3) I (live/lives) with my parents in (a/the) house near the city centre

4) I (have/has) got a sister but she (doesn't/don't) live in (a/the) house

5) She's (a/an) architect and she (work/works) in London

6) (His/Her) job is very interesting

7) My parents (is/are) teachers in the school

8) My mum (teach/theacher) French

9) My dad is (a/an) art teacher adn he (paints/paint) in (his/her) free time