Question 1
Modular ArithmeticIf {x: 2 ≤ x ≤ 18; x ∈ integer} and 7 + x = 4(mod 9), find the highest value of x.
- A.2
- B.5
- C.15
- D.18
Show the answer and explanation
Answer: C (15)
Explanation
7 + x ≡ 4 (mod 9) gives x ≡ 6 (mod 9), so x = 6 or 15 in the range. The highest is 15.