Did you run each software listed in this support article?

You can too open the Programs and Features list in the Control Panel and check if you find Ask. Then you can uninstall it.

thanks Banban,but it's not listed in programs and features

Could you describe where Ask is showing up? For example:

• When you use Firefox's search bar to run a search, instead of getting your preferred search engine, you get results on Ask?
• When you click the Home button or open a new window (Ctrl+n), instead of getting your preferred home page, you get an Ask page?
• When you click the "+" button or press Ctrl+t to open a new tab, instead of getting the usual Firefox new tab page, you get an Ask page?

That would give us a better idea of what to suggest next, in addition to cleaning your computer of Ask-related programs.