# Frequent question: How do you know if a linear transformation is injective or surjective?

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## How do you know if a transformation is injective or surjective?

Testing surjectivity and injectivity

To test injectivity, one simply needs to see if the dimension of the kernel is 0. If it is nonzero, then the zero vector and at least one nonzero vector have outputs equal 0W, implying that the linear transformation is not injective.

## How do you tell if a linear transformation is surjective?

A transformation T mapping V to W is called surjective (or onto) if every vector w in W is the image of some vector v in V. [Recall that w is the image of v if w = T(v).] Alternatively, T is onto if every vector in the target space is hit by at least one vector from the domain space.

## How do you know if a linear transformation is injective?

A linear transformation is injective if the only way two input vectors can produce the same output is in the trivial way, when both input vectors are equal.

## What is Injective and Surjective in linear transformation?

Theorem. If V and W are finite-dimensional vector spaces with the same dimension, then a linear map T : V → W is injective if and only if it is surjective. In particular, ker(T) = {0} if and only if T is bijective. … To find an isomorphism from a vector space V of dimension n to F, choose some basis v1,…,vn of V .

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## How do you know if a matrix is injective?

Let A be a matrix and let Ared be the row reduced form of A. If Ared has a leading 1 in every column, then A is injective. If Ared has a column without a leading 1 in it, then A is not injective.

## How do you find the Injective function?

To show that a function is injective, we assume that there are elements a1 and a2 of A with f(a1) = f(a2) and then show that a1 = a2. Graphically speaking, if a horizontal line cuts the curve representing the function at most once then the function is injective.

## Can a linear transformation be injective but not surjective?

(Fundamental Theorem of Linear Algebra) If V is finite dimensional, then both kerT and R(T) are finite dimensional and dimV = dim kerT + dimR(T). If dimV = dimW, then T is injective if and only if T is surjective.

## Can a matrix be injective but not surjective?

For square matrices, you have both properties at once (or neither). If it has full rank, the matrix is injective and surjective (and thus bijective).

## Is T an injective linear map?

2. Let T:V→W T : V → W be a linear map between vector spaces. Then: T is injective⟺Ker(T)={0V}.