SAT Math Multiple Choice Question 13: Answer and Explanation

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Question: 13

3. If i = , what is the product of (4 + 7i) and ?

  • A. 16 - i
  • B. 14 + i
  • C. 2 - 8i - 14i2
  • D.

Correct Answer: A

Explanation:

A Use FOIL to multiply the two binomials together. The expression becomes 4 - 8i + 7i - 14i2. Simplify the result by multiplying through where you can to get 2 - 8i + i - 14i2. To combine the i terms, multiply 8 by to get . Now the expression is 2 - i + i - 14i2, which can be further simplified to 2 - i - 14i2. Substitute -1 for i2 and combine like terms: 2 - i + 14 = 16 - i, which is (A).

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