I think Khan Academy's exercices accept fractions as an answer. That may be why it does not recognize the infinite decimal. Here are two example on how to convert repeating decimals to fraction:

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We consider the quantities S (for Saima) and B (her brother). We know that the ratio of S/B=50%=1/2. The ratio B/S then equals to 2/1, or 200%. Mathematically, we're considering the inverse of the ...

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3. Percentage Word Problem

The exponent only applies for the term it is attached to. You would need parentheses to include the minus sign.

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3. help with multiplying a negative and variable with an exponent

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That limit is the definition of a derivative. Here's an example with f(x)=4x^2:

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Personnally, I've learned hyperbolas that way: When the 1 is positive, the hyperbola is horizontal, and when it's negative, it's vertical. If we consider a vertical hyperbola, we can rewrite its eq...

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3. Hyperbola something wrong for me