как это сократить 64 / корень из 2

Неоюходимо вставить или Could или Was able to или Could not. 1. I … finish my homework before 7 pm yesterday. 2. My son … talk when he was only 18 months old. 3. - … (you) play piano before you came to our music school? - I … (not) play very well. 4. We … get ready for the performance in spite of the lack of time. 5. When my sister was only five years old, she … swim very well. One day she … swim across our river.

Человек на отрезке S метров делает n шагов .По какой формуле можно рассчитать длину шага x ?