Question

calcule A4,2 + A9,1 + 3.A7,6

Answer 1

$A_{4,2}+A_{9,1}+3.A_{7,6}\\\\\frac{4!}{(4-2)!}+\frac{9!}{(9-1)!}+3.\frac{7!}{(7-6)!}\\\\\frac{4!}{(2)!}+\frac{9!}{(8)!}+3.\frac{7!}{(1)!}\\\\\frac{24}{2}+\frac{9\;.\;8!}{8!}+3\;.\;7!\\\\12+9+3\;.\;5040\\\\21+15120\\\\15141$