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Example Questions
Example Question #51 :Linear Mapping
is the set of all two-by-one matrices - that is, the set of all column matrices with two entries.
Let. Define a linear mappingas follows:
.
True or false:is one-to-one and onto.
False;is one-to-one but not onto
False;is onto but not one-to-one
False;is neither one-to-one nor onto
True
False;is neither one-to-one nor onto
The domain and the codomain ofare identical, sois one to one if and only if it is onto.
A necessary and sufficient condition forto be one-to-one is that the kernel ofbe. In, the zero element is, and this condition states that if
, then
Thus, we can prove thatis not one-to-one - and not onto - by finding a nonzero column matrixsuch that.
Set. Then
There is at least one nonzero column matrix in the kernel of, sois not one-to-one or onto.
Example Question #52 :Linear Mapping
is the set of all polynomials of finite degree in.
Define a linear mappingas follows:
.
True or false:is a one-to-one and onto linear mapping.
False:is onto but not one-to-one.
False:is neither one-to-one nor onto.
True
False:is one-to-one but not onto.
False:is onto but not one-to-one.
The domain and the codomain are both of infinite dimension, so it is possible forbe one-to-one, onto, both, or neither.
is one-to-one if and only if
implies.
Letand
Then
and.
Since
,但,is not one-to-one.
Now let, where finitely manyare nonzero.If
,
then
is therefore onto.