I don't understand why I can't use "to be locked up" instead of "to locked up" mentioned in this right sentence "I've often wondered what it would be like to locked up in a house for twelve weeks with ten strangers."
"to be locked up" The is the simple past passive form:
"He was locked up by the police."
"to locked up" - this is wrong = locked is the past participle.
"To lock up" this is the active form of the verb, "The police locked him up."
He was locked up by the police.
"The police locked him up."