用动词不定式及它的否定形式造三个句子

用动词不定式及它的否定形式造三个句子
(1) 三个动词不定式肯定
To work out this difficult problem in three days is impossible
=It is impossible towork out this difficult problem in three days
To learn English so well is of great importance to us all
=It is of great importance to us all tolearn English so well i
To swim across the river is very easy for the little boy
=It is very easy for the little boy toswim across the river
(1) 三个动词不定式否定
Our teacher often tells us not to be late for school
His parents want him not to play with those bad boys
The girls are told not to go out alone in the evening /at night