could someone explain me please why 2x(3+x)(3-x) = -2x(x+3)(x-3) ?

Hallo "Anonymous",

(x-3) = - ( 3-x)   

2x(3+x)(3-x) = -2x(3+x) *(-(3-x))                 (-) * (-) = (+)

                        = + 2x(3+x)(3-x)

Gruß radix !