Answer :
1. (a + 2)(b - 9) = 0
If the product of two numbers is given to be 0, then either of the number is equal to 0
⇒ a + 2 = 0 , b - 9 = 0
⇒ a = -2 , b = 9
Therefore, The correct option is b. a = -2, b = 9
2. (x - 9)(y + 4) = 0
If the product of two numbers is given to be 0, then either of the number is equal to 0
⇒ (x - 9) = 0 , (y + 4) = 0
⇒ x = 9 , y = -4
Therefore, The correct option is d. x = 9, y = -4
3.
The sum of an even number and an even number
Since, The sum of an even number and an even number is always even number. So, TRUE
The sum of an odd number and an odd number
Since, The sum of an odd umber and an odd number is not and= odd number. So, FALSE
The sum of a prime number and a prime number
FALSE. Counter Example : 3 + 5 = 8 , 8 is not a prime.
None of these are an example of the closure property
First part is an example of closure property. So, FALSE
Therefore, The correct option is a.
4.
The product of a prime number and a prime number
FALSE, Counter Example : 3 × 5 = 15 , 15 is not a prime.
The product of a whole number and a whole number
TRUE
The product of a negative number and a negative number
FALSE, Counter Example : - 3 × - 5 = 15 , 15 is not a negative number.
The product of a natural number and a natural number
TRUE
Therefore, The correct options are : b. and d.
