「因乜解究」and 「有冇解救」are two different phrase.
in「因乜解究」:
「解」refer to 「解釋」(explain)
「究」 refer to「究因 (究其原因)」( investigate the reason)
Example:「(因乜解究)墻上有啲咁恐怖嘅畫嘅？」~「 (what is the explanation and reason = why) the wall has such horrible drawings on it?」
in「有冇解救」:
「解」refer to 「解決」( resolve)
「救」refer to 「拯救」(save)
Example:
「唔知搞成噉，(仲有冇解救) 呢？」~ 「Don't know at this point,( is there still a way to resolve and save it ? = is there still a solution?)
「唔使驚，呢件事(有解救)嘅！」~「Don't worry, this situation ( has a way to resolve and save = has a solution)
In the lyric of 陳浩德's old song 「相思淚」[www.topictimes.com] ( 0:53)
There's one verse: 「因乜(解究)書信都未曾有？」~
「for what (reason ) there is still no letter?」
It make no sense to write 「因乜(解救)書信都未曾有」~ 「for what (solution ) there is still no letter?)
in「因乜解究」:
「解」refer to 「解釋」(explain)
「究」 refer to「究因 (究其原因)」( investigate the reason)
Example:「(因乜解究)墻上有啲咁恐怖嘅畫嘅？」~「 (what is the explanation and reason = why) the wall has such horrible drawings on it?」
in「有冇解救」:
「解」refer to 「解決」( resolve)
「救」refer to 「拯救」(save)
Example:
「唔知搞成噉，(仲有冇解救) 呢？」~ 「Don't know at this point,( is there still a way to resolve and save it ? = is there still a solution?)
「唔使驚，呢件事(有解救)嘅！」~「Don't worry, this situation ( has a way to resolve and save = has a solution)
In the lyric of 陳浩德's old song 「相思淚」[www.topictimes.com] ( 0:53)
There's one verse: 「因乜(解究)書信都未曾有？」~
「for what (reason ) there is still no letter?」
It make no sense to write 「因乜(解救)書信都未曾有」~ 「for what (solution ) there is still no letter?)