an=a(n-1)+a(n+1)/2
a10=(a9+a11)/2=44/2=22 a20=(a19+a21)/2=104/2=52
a10+a20=22+52=74
2/3x=20
20 10 2
x= ------ = ------- = 3----
2/3 3 3
D(y)∈R, т.к D<0
y`=(2x+2)/2√(x²+2x+5)=(x+1)/√(x²+2x+5)=0
x+1=0
x=-1
_ +
----------------------------(-1)-----------------------
min
ymin=√(1-2+5)=√4=2
(-1;2)
C^3/4*c^1/4=c^(3/4+1/4)=c. Ответ : c.