～たら いかがですか

When to use

Polite, formal suggestion - "how about...?" - much more formal than たらいい/ばいい, used with someone you should be respectful toward.

Explanation

The ～たら いかがですか grammar point is used to make polite suggestions, ask for opinions, or imply that something would be good or desirable if the condition is met. The formation differs depending on whether it is used with a verb, い-adjective, な-adjective, or noun.

• 図書館としょかんに行いったらいかがですか。

  How about going to the library?

  Toshokan ni ittara ikaga desu ka.

• 寒さむかったらカーディガンを着きるのはいかがですか。

  How about wearing a cardigan if it's cold?

  Samukattara kaadigan wo kiru no wa ikaga desu ka.

• 部屋へやが暗くらかったら照明しょうめいを付つけるのはいかがですか。

  What if you turn on the light if the room is dark?

  Heya ga kurakattara shoumei wo tsukeru no wa ikaga desu ka.

• 自分じぶんの意見いけんだったら他人たにんに聞きくのはいかがですか。

  How about asking others if it's your own opinion?

  Jibun no iken dattara tanin ni kiku no wa ikaga desu ka.

Should (Advice / Expectation)

• ～たらいい〜tara iiN4Expressing a desire or suggestion for a particular…
• ～ばいい〜ba iiN4Express a suggestion or advice; 'should', 'it would be…
• ～ことだ〜koto daN3Expresses advice or recommendation; 'should', 'it is…
• ～はずだ〜hazu daN3Expresses an expectation, 'should' or 'it is supposed to'.
• ～ものだ〜mono daN2Expresses something natural or expected; 'it is normal…
• ～といい〜to iiN4Express a wish or hope; 'I hope', 'it would be good if'.
• Verb たほうがいい〜ta hou ga iiN4Used to give advice or make a suggestion to someone -…
• ～たら どうですか〜tara doudesukaN4Express a suggestion or advice; 'what if', 'how about'…
• ～べきだ〜beki daN3Express an obligation or something that should be done…
• ～に越したことはない〜ni koshita koto wa naiN1Expresses that something is the best or most desirable…

Compare when to use each