Part A:
Given
defined by
but
Since, f(xy) ≠ f(x)f(y)
Therefore, the function is not a homomorphism.
Part B:
Given
defined by
Note that in
, -1 = 1 and f(0) = 0 and f(1) = -1 = 1, so we can also use the formular
and
Therefore, the function is a homomorphism.
Part C:
Given
, defined by
Since, f(x+y) ≠ f(x) + f(y), therefore, the function is not a homomorphism.
Part D:
Given
, defined by
but
Since, h(ab) ≠ h(a)h(b), therefore, the funtion is not a homomorphism.
Part E:
Given
, defined by
, where
denotes the lass of the integer
in
.
Then, for any
, we have
and
Therefore, the function is a homomorphism.
Pay attention in class and you would know
choice D is correct, any number inside the absolute value sign is positive so choice A and C is eliminated, if there is a negative sign in front of the absolute value symbol, the number becomes negative which eliminates choice B. The only choice left is choice D
[ Answer ]
[ Explanation ]
- Simplify:
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- Apply Perfect Square Formula ( = + 2ab + ) a = 5x, b = 2
+ 2 · 5x · 2 + : + 20x + 4
+ 20x + 4