\text { Find an equation for the line tangent to the curve at the point defined by the given value of } t \text {. Also, find the value of } \frac{d^{2} y}{d x^{2}} \text { at this point. } x=3 t^{2}+6, y=t^{6}, t=-1 Write the equation of the tangent line. y= \text { What is the value of } \frac{d^{2} y}{d x^{2}} \text { at this point? } \frac{d^{2} y}{d x^{2}}=