Question

Difficulty: MediumFunction Definitions, Evaluation, and Custom Operators

For all real numbers xx and yy, the custom operation ⊙\odot is defined by x⊙y=x2−2yx \odot y = x^2 - 2y. What is the value of (3⊙2)⊙4(3 \odot 2) \odot 4?

  1. 17Answer
  2. B
    6
  3. C
    -4
  4. D
    9
  5. E
    -7

Answer

17
Following the explicit operator rule x⊙y=x2−2yx \odot y = x^2 - 2y, first calculate the inner expression (3⊙2)=32−2(2)=5(3 \odot 2) = 3^2 - 2(2) = 5. Next, substitute 5 into the outer expression to compute 5⊙4=52−2(4)=25−8=175 \odot 4 = 5^2 - 2(4) = 25 - 8 = 17. Thus, the value 17 is correct.

Step-by-Step Solution

1
Evaluate the inner function expression (3⊙2)(3 \odot 2) using the rule x⊙y=x2−2yx \odot y = x^2 - 2y
3⊙2=32−2(2)=9−4=53 \odot 2 = 3^2 - 2(2) = 9 - 4 = 5
Parentheses dictate that inner custom operations must be evaluated first.
2
Substitute the result of step 1 back into the expression to evaluate 5⊙45 \odot 4
5⊙4=52−2(4)=25−8=175 \odot 4 = 5^2 - 2(4) = 25 - 8 = 17
Applying the custom operator rule with x=5x = 5 and y=4y = 4 computes the final target value.

Key Concept

Custom Operator Evaluation and Order of Operations
Estimated Time:1m 15s
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