При якому значенні c вектори (c; -2) і (c; 8) перпендикулярні

6y²+2y-9y-3+2(y²+5y-5y-25)=2-4y+6y

6y²-7y-3+2y²-50=2+2y

8y²-9y-55=0

d=81+1768=1849; 43

y=9±43/16

y1=-17/8   y2=13/4

1.

1) b₁ = 2*5¹ = 2*5 = 10,   b₂ = 2*5² = 2*25 = 50,   bn = 2*5^n

2) q = b₂ / b₁ = 50 / 10 = 5

3) sn = (b₁ - bn*q)/(1-q) = (10 - 2*5^n * 5) / (1-5) = (10 - 10*5^n)/(-4) = 10 (1 - 5^n) / (-4) = 2,5(1-5^n)

2.

1) q = c₂/c₁ = -5 / (-5/9)   = 9

2) c₈ = c₁ * q^(n-1) = (-5/9) * 9^(8-1) = (-5/9) * 9^7 = -5 * 9^6 = - 2657205