Matematică -algebră- cls. a 6-a

Efectuați:
a)
[tex] {2018}^{2} - 2018 \times 2019[/tex]
b)
[tex] - 2019 \times ( - 2020) - 2019 + 2019 \times ( - 2020)[/tex]
c)
[tex] {2019}^{2} - 2 \times 2019 \times 2020 + {2020}^{2} [/tex]
​