Some pages have figures that do not display correctly

[tarnold17]

Example:

Here's a full list of the pages I found that have figures which are not displaying:

• https://ndcbe.github.io/optimization/notebooks/6/Newton-Methods.html
• https://ndcbe.github.io/optimization/notebooks/6/Quasi-Newton-Methods.html
• https://ndcbe.github.io/optimization/notebooks/6/Globalization.html
• https://ndcbe.github.io/optimization/notebooks/7/Convexity.html
• https://ndcbe.github.io/optimization/notebooks/7/Local-Optimality.html
• https://ndcbe.github.io/optimization/notebooks/7/KKT-Multipliers.html
• https://ndcbe.github.io/optimization/notebooks/7/Constraint-Qualifications.html
• https://ndcbe.github.io/optimization/notebooks/7/Second-Order.html
• https://ndcbe.github.io/optimization/notebooks/7/Interior-Point1.html
• https://ndcbe.github.io/optimization/notebooks/7/Interior-Point2.html