a) (x+a)(x-a) = x²-a² (am folosit formula (a+b)(a-b)=a²-b²)
b) (2x-3y)(2x+3y) = (2x)²-(3y)² = 4x²-9y² (am folosit formula (a+b)(a-b)=a²-b²)
c) (√7 + 2√2)(√7 - 2√2) = (√7 + √8)(√7 - √8) = √7² - √8² = 7-8 = -1 (am folosit formula (a+b)(a-b)=a²-b²)
L-am scris pe 2√2 = √(2²·2) = √8
d) (m-n)(m+n)·(m²+n²) = (m²-n²)(m²+n²) = (m²)²-(n²)² = [tex]m^{4}-n^{4}[/tex]
Pt. primele doua paranteze am aplicat formula (a+b)(a-b)=a²-b². Dupa ce am calculat primele doua paranteze cu formula, aplic din nou formula pt. ultimele doua paranteze ramase.
