Let f (x) be a differentiable function, definite integral (x, 0) (t-1) f (x-t) DT = 0, find f (x)

Let f (x) be a differentiable function, definite integral (x, 0) (t-1) f (x-t) DT = 0, find f (x)

∫{x,0}(t-1)f(x-t)dt=0;
∫{0,x}(x-u-1)f(u)d(-u)=0…… u=x-t;
∫{0,x}(x-1)f(u)du-∫{0,x}uf(u)du=0;
(x-1)∫{0,x}f(u)du=∫{0,x}uf(u)du;
∫{0,x}f(u)du+(x-1)f(x)=xf(x)…… The two ends are derived from X;
f(x)=f'(x)…… (move items and) repeat the previous step;
That is, f '(x) / F (x) = 1; integral: F (x) = C * e ^ X;