To solve the equation \(-x^{2.9} = -3\), we can first multiply both sides by -1 to simplify:
\[ x^{2.9} = 3 \]
Next, we can take both sides to the power of \(\frac{1}{2.9}\) to solve for \(x\):
\[ x = 3^{\frac{1}{2.9}} \]
Calculating this gives us \(x\):
\[ x \approx 2.150 \]
However, none of the provided options (−8.7, 8.7, 87, −87) are close to this value.
From the context of the provided responses, it’s clear that there may have been some misunderstanding in the mathematical manipulation or the expected answers, but under normal algebraic manipulation, the value would not match any of the choices presented.
If the problem expected one of those specific responses, please verify the equation or look for possible typos related to the exponents or values given. The options seem both inappropriate for the roots of the equation you initially provided. The correct answer based on the calculations doesn’t match available options.