Question

Dacă b= 2+4+6+...+78+80, atunci b=?
Vă rog e urgent
Dau coroană

Answer 1

b=2+4+6+.....+78+80
b=2*(1+2+3+....+39+40)
b=2*40*41/2
b=40*41
b=1640

Answer 2

b=2+4+6+....+78+80

Dăm factor comun pe 2.

b=2(1+2+3+...+39+40)

b=2(80×81:2)

b=80×81

b=6480