[Math] Describe the additive inverse of C($-\infty, \infty$)

linear algebravector-spaces

I'm just stuck on this question. How can I represent the additive inverse of all continuous functions?

The additive inverse: For every $\overrightarrow{u}$ in V, there is a vector V denoted by $\overrightarrow{-u}$ such that $\overrightarrow{u}$ + ($\overrightarrow{-u}$) = $\overrightarrow{0}$.

Any help is appreciated.

This is a solution I found to a similiar problem earlier:

Describe the additive inverse of the vector space $P_3$ where $P_3$ is the set of all polynomials of degree 3 or below.
Solution:
$-(a_0 + a_1x + a_2x^2 + a_3x^3) = -a_0 – a_1x – a_2x^2 – a_3x^3$

Best Answer

I'm not sure if this is what you're after, but the additive identity is always given by $0\cdot\mathbf{v}$ for any $\mathbf{v}$ in the vector space.

Proof: $$\mathbf{v} = 1\cdot\mathbf{v}=(1+0)\mathbf{v} = 1\cdot\mathbf{v} + 0\cdot\mathbf{v} = \mathbf{v} + 0\cdot\mathbf{v}$$ Applying $(\mathbf{-v})$ to both sides then yields $\mathbf{0} = 0\cdot\mathbf{v}$

If the additive inverse is what you want instead, then a similar result will show that $(-1)\mathbf{v}$ is the additive inverse for $\mathbf{v}$

Proof: $$\mathbf{v} + (-1)\mathbf{v} = 1\cdot\mathbf{v} + (-1)\mathbf{v} = (1+(-1))\mathbf{v} = 0\cdot\mathbf{v} = \mathbf{0}$$ Again applying $(\mathbf{-v})$ yields $(\mathbf{-v}) = (-1)\mathbf{v}$

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