La exercitiul 18 ai urmatoarele formule
(a+b)(a-b)=a^2-b^2
(a-b)^2=a^2-2ab+b^2
(a+b)^2=a^2+2ab+b^2
foloseste. le!
de exemplu:
18.f)4x-(5x+1)^2=-6(2x-3)^2-x^2-3
4x-(25x^2+10x+1)=-6(4x^2-12x+9)-x^2-3
4x-25x^2-10x-1+24x^2-72x+54+x^2+3=0
78x+58=0
x=58/78=29/39
la modul |x|+|y|=|x+y|
Daca |x|=4 Atunci -4<=x<=4
Daca a/b=c/d atunci bc=ad
