1. **State the problem:** We have the function $$x = \frac{1}{6}t^3 - 5t$$ and need to find:
a) A value of $$t$$ such that $$\frac{dx}{dt} = 27$$.
b) The corresponding value of $$x$$ at that $$t$$.
2. **Find the derivative:** The derivative $$\frac{dx}{dt}$$ represents the rate of change of $$x$$ with respect to $$t$$. Using the power rule:
$$\frac{dx}{dt} = \frac{d}{dt}\left(\frac{1}{6}t^3 - 5t\right) = \frac{1}{6} \times 3t^2 - 5 = \frac{3}{6}t^2 - 5 = \frac{1}{2}t^2 - 5$$
3. **Set the derivative equal to 27 and solve for $$t$$:**
$$\frac{1}{2}t^2 - 5 = 27$$
Add 5 to both sides:
$$\frac{1}{2}t^2 = 32$$
Multiply both sides by 2:
$$\cancel{\frac{1}{2}} \times 2 t^2 = 32 \times 2$$
$$t^2 = 64$$
Take the square root:
$$t = \pm 8$$
4. **Find the corresponding $$x$$ values for $$t = 8$$ and $$t = -8$$:**
For $$t=8$$:
$$x = \frac{1}{6} \times 8^3 - 5 \times 8 = \frac{1}{6} \times 512 - 40 = 85.3333 - 40 = 45.3333$$
Rounded to 1 decimal place:
$$x = 45.3$$
For $$t=-8$$:
$$x = \frac{1}{6} \times (-8)^3 - 5 \times (-8) = \frac{1}{6} \times (-512) + 40 = -85.3333 + 40 = -45.3333$$
Rounded to 1 decimal place:
$$x = -45.3$$
**Final answers:**
- Values of $$t$$ where $$\frac{dx}{dt} = 27$$ are $$t = 8$$ and $$t = -8$$.
- Corresponding $$x$$ values are $$x = 45.3$$ when $$t=8$$ and $$x = -45.3$$ when $$t=-8$$.
Derivative Cubic 01C8C0
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