設函數f(x)具有二階導數,試證明曲線y^2=f(x)的拐點的橫坐標a適合下列關係(f'(a))^2=2f(a)f''(a)

設函數f(x)具有二階導數,試證明曲線y^2=f(x)的拐點的橫坐標a適合下列關係(f'(a))^2=2f(a)f''(a)

證明:y^2=f(x),所以:y=f(x)^1/2y'=1/2f(x)^(-1/2)*f'(x)拐點時y''=1/2*(-1/2)f(x)^(-3/2)*f'(x)*f'(x)+1/2f(x)^(-1/2)*f''(x)=0拐點的橫坐標為a所以1/2f(x)^(-1/2)*f''(a)=1/4f(x)^(-3/2)*[f'(a)]^2f''(a)=1/2f(x)^(…