a6+a8=16 a2*a12=-36 Решите. сам не могу додуматься

Al → Al2O3 → Al2(SO4)3 → Al(OH)3 → KAlO2 → Al(OH)3

В классе 25 учеников. Из них 17 умеют ездить на велосипеде, 13 плавать, а ты8 ходить на лыжах. Ни один из учеников не владеет тремя видами спорта. Все велосипедиста, пловцы, и лыжники имеют по математике оценки 4 или 5. В классе 6 учеников имеют удовлетворительным оценки по математике. Сколько учеников не успевают по математике? Сколько пловцов умеют ходить на лыжах

разность квадратов двух чисел равна 100ю Если из утроенного первого числа вычесть удвоенное двойное число, то получиться 30 найдите эти числа?

Выполните тест. Письменно переведите предложения.

         1. At the Customs House I ... to open my suit-case.

                   a) asked

                   b) was asked

                   c) am asking

         2. The monitor of the group ... next week.

                   a) will be elected

                   b) was elected

                   c) has been elected

         3. They ... since last year.

                   a) have been divorced

                   b) were divorced

                   c) will be divorced

         4. I ... slowly down the street when somebody called me.

                   a)was walking

                   b) am walking

                   c) will be walking

         5. After she ... she felt better.

                   a) had cried

                   b) cries

                   c) has cried

1)    Изучите тему: простые неличные формы глагола- ParticipleI, ParticipleII.

Выполните тест .Письменно переведите предложения.

         1. I felt suddenly small ...beside those immense walls of stone.

                   a) standing

                   b)stood

         2. Generally ...,the problem is not so easy as it seems to be.

                   a) spoken

                   b) speaking

         3. He stood for a while ... my hands.

                   a) holding

                   b) held

         4. Frankly ... I can’t approve of his behaviour.

                   a) speaking

                   b) spoken

         5. He will certainly come if ...

                   a) asked

                   b)asking

         3. Изучите тему : модальные глаголы и их эквиваленты.

Выполните тест. Письменно переведите предложения.

         1....I call you Bob?

                   a) May

                   b) Can

                   c) Could

         2. Why are you late? You ... to have come at 10 a. m.

                   a) were

                   b) can

                   c) may

         3. Don’t make so much noise. We ... wake the baby.

                   a) mustn’t

                   b) can’t

                   c) are to

         4. Their son ... stay up late last night to watch the World Cup on TV.

                   a) could

                  b) was allowed to

                   c) had to

         5. –I’ve got a terrible headache.

             - You ... take an aspirin.

                   a) should

                   b) must

                   c) can