Video help added for Determine whether the critical points correspond to a maximum

We added video help to Determine whether the critical points correspond to a maximum for students who need to see the step move, not just read it.

Why this matters

Some doubts are not about the final answer. They are about the transition: why this line became the next line, why a formula was chosen, or why a shortcut is allowed.

What to do now

• Read the written solution first.
• Watch the video only where the step feels unclear.
• Try the same question again without pausing.

Use the video as a repair tool: watch the confusing part, then come back to solving.