Cevap:
1.) İki kare farkından hesaplarız.
[tex]a^{2}-b^{2} = (a-b).(a+b)\\\\\\2021^{2}-2020^{2}=(2021-2020).(2021+2020)\\\\2021^{2}-2020^{2}=1.4041=4041[/tex]
2.)
[tex](a+b)^{2}=a^{2}+2ab+b^{2}\\(5x+4)^{2}=5x^{2}+2.5x.4+4^{2}\\(5x+4)^{2}=5x^{2}+40x+16[/tex]
a=5 , b=40 , c=16
a+b+c=5+40+16=61
