Windows Security provides built-in security options to help protect your device from malicious software attacks. To access the features described below, tap the Windows Start button, type windows security, select it from the results, and then select Device security.

Notes: If you don't see Go to Microsoft Store on the Activation page, contact your organization's support person.. If you made a substantial hardware changes to your device (such as replacing the motherboard) and you have a valid product key, try to activate Windows by phone.

Note: The TEXT function converts numbers to text, which may make it difficult to reference in later calculations.It’s best to keep your original value in one cell, and then use the TEXT function in another cell. Then, if you need to build other formulas, always reference the original value and not the TEXT function result.

Tip: If your can't get the code by email or phone, you might be able to enter an email address that's different from the one you're trying to recover. Go to the Recover your account page and follow the prompts.

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但如果需要测试多个条件，例如我们假设所有条件都需要为 True 或 False (AND)，或只有一个条件需要为 True 或 False (OR)，或者如果想要检查某个条件是否不 (NOT) 符合你的条件，这时该怎么做呢？这三个函数均可以单独使用，但它们更常见于与 IF 函数成对使用。

Find and download free templates to create documents like calendars, business cards, letters, greeting cards, brochures, newsletters, or resumes.

Download our Formulas tutorial workbook. We've put together a Get started with Formulas workbook that you can download. If you’re new to Excel, or even if you have some experience with it, you can walk through Excel’s most common formulas in this tour.

Here's an example of how to use VLOOKUP. =VLOOKUP(B2,C2:E7,3,TRUE) In this example, B2 is the first argument—an element of data that the function needs to work.For VLOOKUP, this first argument is the value that you want to find.

Tip: If you installed the Microsoft 365 apps as part of a suite, such as Office Home and Student or Microsoft 365, search for the suite name.For stand-alone apps search by the app name, such as Project or Visio. In most cases you can't uninstall an individual app if it's included in your Microsoft 365 suite.