Refer to the first few lines of

Newton's method in optimization - Wikipedia, the free encyclopedia

giving Taylor expansion approximation

F(x+DeltaX)=.........+ 1/2 * F2(X) * DeltaX^2

comes out

F1(X)+F2(X) * DeltaX = 0

Why missing the coefficient 1/2 ? is it a mistake?

thanks.