Question

Qual o valor de A12,4- A7,2? a) 11880 b) 11838 c) 12840 d) 12480 e) 10840

Answer 1

Vamos nessa!

$A_{12,4}-A_{7,2}= \dfrac{12!}{(12-4)!} -\dfrac{7!}{(7-2)!}$

$\dfrac{12!}{8!} -\dfrac{7!}{5!}.\dfrac{8.7.6}{8.7.6}$

$\dfrac{12!}{8!} -\dfrac{8.7.6.7!}{8!}= \dfrac{12!-8!</p><p>.42}{8!}$

$\dfrac{8!.(12.11.10.9-42)}{8!}=12.11.10.9-42$

Agora ficou fácil!

$A_{12,4}-A_{7,2}= 11838$

Alternativa correta: B

Espero ter ajudado!