a) x²-18xy+81y² =
= x^2 -18xy + 9^2 × y^2 =
= x^2 -18xy + (9y)^2 =
= (x-9y)^2
OBS: Folosesti formula de calcul prescurtat:
a^2 - 2ab + b^2 = (a-b)^2
c) 4xy+2x²+2y² =
= 2(2xy +x^2 +y^2)=
= 2(x^2 + 2xy + y^2)=
= 2(x+y)^2
OBS: Folosesti formula de calcul prescurtat:
a^2 + 2ab + b^2 = (a+b)^2