Question

Păreri ? Exista o formulă ?​

Answer 1

Explicație pas cu pas:

1)

$11\cdot(1 + 2 + ... + 9) = 11\cdot \frac{9 \times 10}{2} \\ = 11 \times 45 = 495$

2)

$A_{n}^{k} = \frac{n!}{(n - k)!}$

$\iff A_{4}^{3} = \frac{4!}{(4 - 3)!} = \frac{4!}{(1)!} \\ = 2 \times 3 \times 4 = 24$

numerele sunt:

246, 248, 264, 268, 284, 286,

426, 428, 462, 468, 482, 486,

624, 628, 642, 648, 682, 684,

824, 826, 842, 846, 862, 864