a series of attempts having been made,we came to a wonferful solution to the problem.
你如果使用had been made ,原句就出现两个谓语而没有连词连接,是错句.这是分词的独立主格结构作状语的用法.原句可改成:
After a series of attempts had been made ,we came to a wonferful solution to the problem.把句中的时间状语从句改成状语,就是:
1、删掉连词
2、从句的主语和主句的主语不相同或不相一致,保留下来.(如果一致,主语也删掉.)
3、从句的谓语是被动形式,且动作发生在主句动作前,改成过分made或现分的被动形式having been made,