Question

Aplicind formula (a+b)(a-b)=a la puterea a doua - b la puterea a doua,calculati oral:
a) 101*99
b) 51*49
c) 61*59
d) 102*98
e) 32*28
f) 43*37.

* inseamna imultirea

Answer 1

b) (50+1)(50-1) = 50² - 1² = 2500 - 1 = 2499
c) (60+1)(60-1)
d) (100+2)(100-2)
e) (30+2)(30-2)
f)  (40+3)(40-3)