Linear Algebra : Linear Algebra

Study concepts, example questions & explanations for Linear Algebra

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Example Questions

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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.

Possible Answers:

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

Correct answer:

False;is neither one-to-one nor onto

Explanation:

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.

Possible Answers:

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.

Correct answer:

False:is onto but not one-to-one.

Explanation:

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.

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