Consider the function $m(t)=\frac{-28}{5 t}$.

Angie states that the additive inverse is $p(t)=\frac{28}{5 t}$ and the multiplicative inverse is $r(t)=\frac{-28}{5 t}$. Is one (or both) of Angie's conclusions correct?


AAngie is correct about both inverses.
BAngie is correct about neither inverse.
CAngie is correct about the additive inverse only.
DAngie is correct about the multiplicative inverse only.

Verified Answer :

  • Define the function \(m(t) = -\frac{28}{5t}\).
  • Verify the additive inverse condition: \(m(t) + p(t) = 0\). Since \(-\frac{28}{5t} + \frac{28}{5t} = 0\), \(p(t)\) is correct.
  • Verify the multiplicative inverse condition: \(m(t) \cdot r(t) = 1\). Since \(\left(-\frac{28}{5t}\right) \cdot \left(-\frac{28}{5t}\right) = \frac{784}{25t^2} eq 1\), \(r(t)\) is incorrect.
  • Conclude that Angie is correct about the additive inverse only. \(\boxed{\text{Angie is correct about the additive inverse only.}}\)

Explanation

  1. Understanding Definitions of Inverses

We are given the function \(m(t) = -\frac{28}{5t}\). We need to determine if the proposed additive inverse \(p(t) = \frac{28}{5t}\) and the proposed multiplicative inverse \(r(t) = -\frac{28}{5t}\) are correct.

The additive inverse \(a(t)\) of a function \(m(t)\) is defined such that \(m(t) + a(t) = 0\).
The multiplicative inverse \(m'(t)\) of a function \(m(t)\) is defined such that \(m(t) \cdot m'(t) = 1\).

  1. Checking the Additive Inverse

To check if \(p(t) = \frac{28}{5t}\) is the additive inverse of \(m(t) = -\frac{28}{5t}\), we calculate their sum:
\[m(t) + p(t) = \left(-\frac{28}{5t}\right) + \left(\frac{28}{5t}\right) = 0.\]
Since the sum is 0, Angie is correct about the additive inverse.

  1. Checking the Multiplicative Inverse

To check if \(r(t) = -\frac{28}{5t}\) is the multiplicative inverse of \(m(t) = -\frac{28}{5t}\), we calculate their product:
\[m(t) \cdot r(t) = \left(-\frac{28}{5t}\right) \cdot \left(-\frac{28}{5t}\right) = \left(\frac{28}{5t}\right)^2 = \frac{784}{25t^2}.\]
Since this product is not equal to 1 (for all \(t\)), \(r(t)\) is not the multiplicative inverse. The correct multiplicative inverse would be \(m'(t) = \frac{1}{m(t)} = \frac{1}{-28/(5t)} = -\frac{5t}{28}\). Thus, Angie is incorrect about the multiplicative inverse.

  1. Conclusion

Based on our analysis, Angie is correct about the additive inverse only. The additive inverse \(p(t) = \frac{28}{5t}\) satisfies \(m(t) + p(t) = 0\), while the multiplicative inverse \(r(t) = -\frac{28}{5t}\) does not satisfy \(m(t) \cdot r(t) = 1\). Therefore, the correct conclusion is that Angie is correct about the additive inverse only. The final answer is \(\boxed{\text{Angie is correct about the additive inverse only.}}\)

Examples

In economics, additive and multiplicative inverses are essential concepts. An additive inverse represents a debt that perfectly offsets a specific amount of assets, leading to a net worth of zero. For example, if you have an asset valued at \(v\), the debt \(-v\) acts as its additive inverse. A multiplicative inverse, on the other hand, is crucial in currency conversion or rate adjustment; if a factor \(f\) is applied to a value to scale it, the multiplicative inverse \(1/f\) reverses that scaling effect exactly. Understanding these inverses helps in balancing budgets and normalizing financial data.