Известно что числа 3x-4,2x и 4x+1, взятые в этом порядке, образуют конечную арифметическую прогрессию. Чему равна сумма ее членов ?

В выражении заключите в скобки два последних слагаемых поставив перед скобками а) знак + б) знак - 

a-b+5 

Заранее спасибо! :) 

Вместо инфинитива поставьте глагол в нужном времени.

1. I (to sail) on board the m/v Vyborg last year as an able seaman. 2. The Third Engineer (to keep watch) in the engine-room tomorrow. 3. The Second Officer (to define) the ship's position at the moment. 4. The boatswain (to order) the sailors to paint the hull yesterday. 5. Will you (to take) bearings during your watch? 6. Cadets sometimes (to have) their training on board merchant ships. 7. What is the radio-apprentice doing? — He (to receive) a weather report now. 8. Our electrician (to repair) the pump (насос) last Wednesday. 9. Our captain (to sail) to the Arctic every year. We (to tune) the transmitter at 8 o'clock yesterday.

главная мысль в истории Два брата Е.Шварца