(x+5y)^2-(x-5y)^2 x^2+10xy+25y^2-x^2+10xy-25y^2 10xy
_____________ = ___________________________ = _____ =10 x
y y y
(5x+3y)^2-(5x-3y)^2 25x^2+30xy+9y^2-25x^2+30xy-9y^2 60xy
______________ = ___________________________ = _____ = 60x
y y y
(7x+y)^2-(7x-y)^2 49x^2+14xy+y^2-49x^2+14xy-y^2 28xy
____________ = __________________________ = ____ = 28
x y xy xy
Помогла?)