对x的偏导数是6x+1 ---> f(x,y) = 3x^2+x+C(y)
f(x,2x)=x^2+3x -----> 3x^2+x+C(2x) = x^2+3x ------> C(2x) = -2x^2 + 2x
------> C(x) = x-1/2x^2 -----> C(y) = y - 1/2y^2
f(x,y) = f(x,y) = 3x^2+x+y - 1/2y^2
f(x,y)其对y的偏导数 = 1 -2y
对x的偏导数是6x+1 ---> f(x,y) = 3x^2+x+C(y)
f(x,2x)=x^2+3x -----> 3x^2+x+C(2x) = x^2+3x ------> C(2x) = -2x^2 + 2x
------> C(x) = x-1/2x^2 -----> C(y) = y - 1/2y^2
f(x,y) = f(x,y) = 3x^2+x+y - 1/2y^2
f(x,y)其对y的偏导数 = 1 -2y