# Proving vector space, associativity

• karnten07
Therefore, the expressions are not equal. In summary, the attempt to show exp(b.c.lnx) = b.exp(c.lnx) is not valid as it leads to expressions that are not equal and a counter-example can easily be found.
karnten07

## Homework Statement

Im doing a problem where I am trying to show that an abelian group with a scalar multiplication is a vector field. I am trying to show associativity right now and just have a question:

im trying to show that exp(b.c.lnx) = b.exp(c.lnx)

But I am not very sure of my logs and exp's laws, not sure that they are even equal. Any pointers guys?

## The Attempt at a Solution

They wouldn't be equal.

Since $$e^x$$ and $$\ln x$$ are inverses of each other, $$e^{\ln x} = x$$. Therefore, your expressions can be simplified to $$x^{bc} = bx^c$$ which are not equal.

Also, a simple counter-example shows the same result: Taking $$x=3, b=2, c=1$$ we have $$3^{1\cdot 2}=2\cdot 3^1$$ which is obviously not true.

## 1. What is a vector space?

A vector space is a mathematical structure that consists of a set of objects, called vectors, that can be added together and multiplied by scalars, such as real numbers. This structure follows specific rules, including associativity, to be considered a vector space.

## 2. How is associativity defined in a vector space?

Associativity in a vector space means that the order of operations does not matter when adding or multiplying vectors. In other words, when adding or multiplying three or more vectors, the grouping of the operations does not affect the final result.

## 3. Why is associativity important in a vector space?

Associativity is important in a vector space because it ensures that the operations of addition and multiplication are well-defined and consistent. This allows for the use of these operations in various mathematical proofs and applications.

## 4. How is associativity proven in a vector space?

To prove associativity in a vector space, we must show that for any three vectors, u, v, and w, the following equation holds: (u + v) + w = u + (v + w). This can be done by using the properties of vector addition and scalar multiplication and showing that both sides of the equation result in the same vector.

## 5. What are some real-life examples of associativity in vector spaces?

One example of associativity in everyday life is in the measurement of time. The addition of time intervals is associative, meaning that the total time elapsed is the same regardless of the order in which the intervals were added. Another example is in the combination of forces in physics, where the order of combining the forces does not affect the final result.

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