Suppose the true population regression function is Y=0+1X+2X2.

Suppose the true population regression function is Y=β0+β1X+β2X2. If X>0, β1<0 and β2>0, then in a graph with Y on the y-axis and X on the x-axis, the shape of the curve will be

Upward sloping with an increasing slope

Shaped like a U

Shaped like an upside-down U

Downward sloping with a decreasing slope