4.Calculeaza dupa model :
Model : 51² = (50+1)² = 50² + 2×50×1+1²=2500+100+1=2601
a) 51²
b)23²
c)49²

7.Calculeaza dupa model :
Model : 28×32 = (30-2)(30+2) = 30²-2²=900-4 = 896

a)28×32
b)49×51
c) 37×23
d)102×98
e)105×95
f)1980×2020

8.Calculeaza , folosind formula : (a+b)(a-b)=a²-b²

a) (x+1)(x-1)
b) (x+2)(x-2)
c) (x+3)(x-3)
d) (x+5)(x-5)