There are some common reasons that an answer may look correct to you, but has been marked incorrectly. This gives an overview of some of these reasons.
Answers with powers
Powers must be entered using our online keyboard or a regular keyboard using the keyboard shortcut '^'.
If the student has used a special character it will not be accepted.
If the student's power looks smaller than the one given as a correction, they may have entered a power of a power ('^^' instead of '^'), rendering the answer incorrect.
Are the brackets present? Are there commas or brackets missing? Is the comma mistakenly a full stop? Is there an extra bracket? All of these will cause a coordinate answer to be marked incorrectly.
When giving multiple coordinates, the order given does not matter as long as they are in the format (x,y)
Answers with a Multiplication Sign
A common mistake is for a student to use an 'x' rather than the multiplication sign from the keyboard. 'multiplied by' must be entered using the 'times sign' from the on-screen keyboard: