Question

Алгебра
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Answer 1

Объяснение:

1)

$\frac{P_7}{P_4}=\frac{7!}{4!} =\frac{4!*5*6*7}{4!}=5*6*7=210.$

2)

$\frac{A_6^5}{P_7}=\frac{\frac{6!}{(6-5)!} }{7!} =\frac{\frac{6!}{1!} }{7!}=\frac{6!}{7!}=\frac{6!}{6!*7}=\frac{1}{7}.$

3)

$1+\frac{P_8}{P_7} +\frac{P_5}{P_6}=1+\frac{8!}{7!} +\frac{5!}{6!} =1+\frac{7!*8}{7!}+\frac{5!}{5!*6} =1+8+\frac{1}{6}=9\frac{1}{6} .$

4)

$\frac{P_9}{P_7} -\frac{P_7}{P_5}-2=\frac{9!}{7!}-\frac{7!}{5!} -2=\frac{7!*8*9}{7!}-\frac{5!*6*7}{5!}-2=8*9-6*7 -2=72-42-2=28.$