Question

 Calculati :
(x+5)(x-5)-$(x-7)^{2}$

Answer 1

poi la primele doua paranteze faci inmultirea fiecare termen cu fiecare : (x+5)(x-5)=x*x+x*(-5)+5*x+5*(-5)=x²-5x+5x-25= x²-25 sau folosind  formula (x+5)(x-5)=x²-25

iar a doua paranteza se face cu formula :(x-a)=x²-2*x*a+a²

(x-7)=x²-2*x*7+7²=x²-14x+49

si finalul : x²-25-(x²-14x+49)=x²-26-x²+14x-49=14x- 75