Hi, this is my first time posting. I need help with this problem:

Suppose the equation for an ellipse is given by

Find so that the eccentricity is 0.75

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I know that eccentricity is defined as , making and . However, if I plug these values into the Pythagorean theorem, I get (which is obviously incorrect, right? We're dealing with real numbers).

How do I solve this problem? Thanks in advance.