Răspuns:
a=1010
b=-2018/4
Explicație pas cu pas:
a=-1+2-3+4-5+6-7+8-...-2019+2020
-1+2=1
-3+4=1
-5+6=1
-7+8=1
-2019+2020=1
=> a=1+1+1...+1 de 2020/2 ori
=> a=1010
b=2+4-6+8-10+12-14+...-2018+2020
2+4-6=0
8-10=-2
12-14=-2
-2018+2020=-2
=> b=-2-2-2...-2 de 2018/4
=> b=-2018/4
