Выберите выражения
1) (38+2(x∗−1)
2) 3a−2b
3) 8=8
4) 18x=2x−3
5) 7⋅(2c−a)

Childhood and youth yuri gagarin was born in 1934. his parents had four children in total. in september 1941 he went to school, but soon the village where he lived was occupied by the german army. only in 1943 yuri continued his studies at school. in 1951 gagarin entered the saratov industrial technical school and later joined local flying club. he completed his studies at the technical school with distinction, achieved much success and performed his first flight on a yak-18 trainer aircraft. in 1955 yuri gagarin joined the soviet army. later he was given the qualification of a military pilot. in 1959 gagarin was selected for the soviet space program. he underwent special training which tested his physical and psychological endurance. gagarin was chosen out of 20 candidates upon the commission's decision.

ответ:

2,4,7 я думаю

объяснение:

выражением называется одна или несколько величин (чисел и букв), соединенных между собой знаками действий: сложения, вычитания, умножения и деления, а также извлечения корня и возведения в целую степень (причём показатели корня и степени должны обязательно быть целыми числами) и знаками последовательности этих действий (обычно скобками различного вида). количество величин, входящих в выражение, должно быть конечным

А²-1/1-а=(а-1)(а+1)/1-а=(а-1)(а+1)/ -(а-1)= -(а+1)= -а-1