Question

(x+y/2)^2-(x-y/2)^2=xy Верно ли равенство ?Докажите

Answer 1

[(x+y)/2-(x-y)/2]*[(x+y)/2+(x-y)/2]=(x+y-x+y)/2*(x+y+x-y)/2=2y/2*2x/2=xy
xy=xy