Question

Математика 100 баллов​

Answer 1

1)

А)C(4;8)=8!/(4!(8-4)!)=1*2*3*4*5*6*7/(1*2*3*4*1*2*3*4)=70

Б)C(6;70=7!/(6!*1!)=7

В)C(1999;1999)-C(1;1999)=1999!/(1999!*0!)-1999!/(1!*1998!)=

=1-1999=-1998

Г)C(3;6)-C(2;6)=6!/(3!*3!)-6!/(2!*4!)=20-15=5

Д)C(4;9)+C(3;9)=9!/(4!*5!)+9!/(3!6!)=126+84=210

Е)=1+10+10+5+1=27

2)С(4;30)=30!/(4!*26!)=27*28*29*30/(1*2*3*4)=27405

3)3*(x+1)!/(2!(x+1-2)!)-2x!/(x-2)!=x

1.5x(x+1)-2x(x-1)=x

1.5x^2+1.5x-2x^2+2x=x

-0.5x^2+2.5x=0

0.5x(-x+5)=0

x1=0-не подходит

x2=5