设f(u)具有二阶连续导数,且g(x,y)=f(y/x)+yf(x/y),求x²(δ²g/δx²)-y²(δ²g/δy²)

问题描述:

设f(u)具有二阶连续导数,且g(x,y)=f(y/x)+yf(x/y),求x²(δ²g/δx²)-y²(δ²g/δy²)

复合函数求偏导啊g对x一阶导数,-f'(y/x)*y/x^2+f'(x/y)g对y一阶导数,f'(y/x)/x+f(x/y)-f'(x/y)/y所以g对x二阶偏导,f''(y/x)*y^2/x^4+2f'(y/x)*y/x^3+f''(x/y)g对y二阶偏导,f''(y/x)/x^2+f''(x/y)*x/y^3所以所求的式...