If a and b are two odd positive integers, by which of the following integers is (a4 - b4) always divisible?
3
6
8
12
If x * y = (x + 3)2 (y - 1), then the value of 5 * 4 is
192
182
180
172
A.
192
Given,
x * y = (x + 3)2 (y - 1)
5 * 4 = ( 5 + 3)2 (4 - 1)
= 82 x 3 = 64 x 3 = 192
If a and b are odd numbers, then which of the following is even?
a + b + ab
a + b - 1
a + b + 1
a + b + 2ab