设由参数方程?x=t^2/2,y=1-t,确定的函数为y=y(x)，求d^2y/dx^2

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X=t^2/厅前陵2
Y=1-t
dy/dx=(dy/dt)/(dx/dt)
=(-1)/扮戚t
=-1/t
d^2y/dx^2=d/悔脊dx(dy/dx)
=(d/dt(dy/dx))/(dx/dt)
=(1/t^2)/t
=1/t^3

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