d^2y/dx^2 + y = 0最后因该是y=?,实在是一窍不通

d^2y/dx^2 + y = 0最后因该是y=?,实在是一窍不通
d^2y/dx^2 + y = 0
最后因该是y=?,实在是一窍不通

d^2y/dx^2 + y = 0最后因该是y=?,实在是一窍不通
y=-y'' d^2y/dx^2是二阶导的意思,d^2y是对y求两次导,dx^2是x一阶导的平方