If X = 12 , Which of the following has the maximum value ?

1. ( x – 3 )
2. ( x – 7 ) ( x – 9 )
3. ( x – 5 ) ( x – 3 )
4. ( x – 8 ) ( x – 7 )

Answer: ( x – 5 ) ( x – 3 )

Explanation: x – 3= 12 – 3= 9(x – 7)(x – 9)=(12 – 7)(12 – 9)=5 × 3=15(x – 5)(x – 3)=(12 – 5)(12 – 3)=7 × 9=63 (answer:)(x – 8)(x – 7)=(12 – 8)(12 – 7)=4 × 5=20x – 2=12 – 2=10