What did harry see while hiding in the cabinet at a shop in knockturn alley?

Im gonna say he saw the hand of glory harry also saw that luicius was selling the potions 

He particularly important objects he saw was the hand of glory (which Malfoy shows interest in and later buys and uses to sneak death eaters into the castle)

Decontamination of materials.

You're asking in the ap section, so i'll give the ap calculus-style answer. alternatively, you can find the vertex of the parabola and use the "y"-coordinate as the answer.

the maximum height can occur at a critical number, that is, a number  such that  .

the derivative of  can be calculated as follows:



find a value of  that is a zero of the derivative:


this is parabola that is opening downward; we can assume there is a maximum at  .

to find that maximum, calculate  .