Question

2) Urmatoarele calcule contin greseli.Depistați-le!
a) (x+a)(x-a)=x²+a²;
b) (y+b)(b-y)=y²-b²;
c) (-z-c)(z+c)=z²-c²

Answer 1

vezi daca te ajuta
a) (x+a)(x-a)=x²+a²;
(x+a)(x-a)=x×x+x×(-a)+a×x+a×(-a)=x²-xa+xa-a²=x²-a²
b) (y+b)(b-y)=y²-b²;
(y+b)(b-y)=y×b+y×(-y)+b×b+b×(-y)=yb-y²+b²-yb=-y²+b²
c) (-z-c)(z+c)=z²-c²
(-z-c)(z+c)=(-z)×z+(-z)×c+(-c)×z+(-c)×c=-z²-zc-cz-c²=-z²-2zc-c²