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Answer:
k = 2
Explanation:
The geometric mean theorem for the altitude tells you ...
ON = √(OL·OM)
ON² = OL·OM . . . . . square both sides
4² = 8·k . . . . . . . . substitute values
k = 16/8 = 2 . . . . divide by the coefficient of k
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Additional comment
The geometric mean theorem for the legs tells you ...
MN = √(MO·ML) ⇒ l = 2√5
LN = √(LO·LM) ⇒ m = 4√5
These relations come from the fact that corresponding sides of the right triangles are proportional. (All of the triangles are similar.)