Response: 8n
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Clarification:
The two sides, 4n+5 and 5n+6, comprise terms 4n and 5n which total to 9n. We require 8n to add to this to achieve 17n. In simpler terms, 4n + 5n + 8n = 9n + 8n = 17n
That is the reason why the outcome is 8n. There are no additional terms because the "+5" and "+6" in the two given expressions (4n+5 and 5n+6) sum to 5+6 = 11, matching what we aim for in the perimeter expression 17n + 11
Side 1 = 4n + 5
Side 2 = 5n + 6
Side 3 = 8n
Perimeter = (side1) + (side2) + (side3)
Perimeter = (4n + 5) + (5n + 6) + (8n)
Perimeter = 4n + 5 + 5n + 6 + 8n
Perimeter = (4n + 5n + 8n) + (5 + 6)
Perimeter = 17n + 11
So this confirms we possess the correct expression for the third side that is missing.