Answer:
19 or 26
Explanation:
You want the value of 3n² -8n -9, given that n(n -3) = 10.
Values of n
We recognize that 10 = 5·2 and that these factors differ by 3. This means n(n -3) = 10 is equivalent to saying n ∈ {-2, 5}.
Expression in n
The value of 3n² -8n -9 will be one of ...
(3n -8)n -9 = (3(-2) -8)(-2) -9 = (-14)(-2) -9 = 19 . . . . for n = -2
or
(3(5) -8)(5) -9 = (7)(5) -9 = 26 . . . . . . . for n = 5
The expression 3n² -8n -9 will be either 19 or 26.
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