Задача 31654 ...

sova

2018-12-07 09:23:56

1.
(x/y)+9*(y/x)-6=(x^2+9y^2-6xy)/(xy) =(x-3y)^2/(xy)

1/xy при x=sqrt(5); y=sqrt(0,2) равно 1.
2
с_(1)=4*1-(3/1)=1
с_(2)=4*2+(3/2)=9,5
с_(3)=4*3-(3/1)=11
с_(4)=4*4+(3/24=19/4
О т в е т. 1) 6 целых (1/3)

3.
По формуле
a_(n)=a_(1)+d*(n-1)
4.
По формуле
a_(n)=a_(1)+d*(n-1)

a_(14)=-7+1,1*(14-1)=7,3

По формуле
S_(n)=(a_(1)+a_(n))*n/2
S_(14)=(-7+7,3)*14/2=0,3*7=2,1

5.
c_(2)=c_(1)-1=-3-1=-4
c_(3)=c_(2)-1=-4-1=-5
c_(4)=c_(3)-1=-5-1=-6
c_(5)=c_(4)-1=-6-1=-7

6.

a_(1)=-8
a_(2)=-5
d=a_(2)-a_(1)=-5-(-8)=3

По формуле
a_(n)=a_(1)+d*(n-1)

a_(81)=a_(1)+d*(81-1)=-8+3*80=240-8=232

7.

a_(2)=a_(1)-0,3=2,6-0,3=2,3
a_(3)=a_(2)-0,3=2,3-0,3=2
...
a_(17)=...

S_(17)=(a_(1)+a_(17))*17/2

8.
a_(1)=-55
d=-46-(-55)=9
a_(7)=-55+9*7=8
S_(7)=(-55+8)*7/2=-329/2

9.
a_(1)=1,4+0,3=1,7
a_(17)=1,4+0,3*17=

S_(17)=(a_(1)+a_(17))*17/2

10.
d=12-10=2
x=6+2=8
О т в е т. 8