Răspuns:
R:458
Explicație pas cu pas:
Aflati numărul abc, stiind că
(aa --1) x (bb-4×a+c) = 2021.
(10a+a-1)(10b+b-4a+c)=2021
(11a-1)(11b-4a+c)=2021
121ab-44a²+11ac-11b+4a-c=2021
11a(11b-4a+c)-(11b-4a+c)=2021
(11b-4a+c)(11a-1)=43×47
11a-1=43
11a=44
a=4
11b-4a+c=47
11b-4×4+c=47
11b+c=47+16=63 ce Nr ×cu 11 dă sub 66? 5
11b+c=55+8=63
b=5. c=8
