Question

Calculati suna: a) 1+2+3+4+5.......+2020= b).2+4+6+2018+2019​

Answer 1

Răspuns:

a) 2041210

b) 1021109

Explicație pas cu pas:

Folosim formula Sumei lui Gauss

1 + 2 + .. + n = n(n+1)/2

• 1 + 2 + .. + 2020 =

= 2020(2020 + 1)/2

= 1010×2021

= 2041210

• 2 + 4 + .. + 2018 + 2019

= 2(1 + 2 + .. + 1009) + 2019

= 2×1009×1010/2 + 2019

= 1009×1010 + 2019

= 1019090 + 2019

= 1021109

Answer 2

a). Folosim suma lui Gauss

1+2+3+4+5+...+2020=ultimul numar(2020) * următorul numar(2021) supra 2=(2020*2021)/2=4082420/2=2041210

b).2+4+6+2018+2019=12+4037=4049