A rectangle is inscribed under the curve y = e^-X^2, with its base along the x-axis. Determine the rectangle of largest area given that the base cannot exceed 4 units.
did you draw a diagram?
notice that the height of the inscribed rectangle will be $\displaystyle e^{-x^2}$ and the base will be $\displaystyle 2x$, where $\displaystyle x$ is the distance from the y-axis to the bottom right corner of the rectangle.
What is the formula for the area? This is what you must maximize