...........................
Т=V+AR.........................
A1=56
S4=a1(q^4-1)/(q-1)
56(q³+q²+q+1)=8736
q³+q²+q+1=156
q³+q²+q-155=0
q²(q-5)+6q(q-5)+31(q-5)=0
(q-5)(q²+6q+31)=0
q-5=0
q=5
q²+6q+31=0
D=36-124=-88 нет решения
Ответ q=5
Решение
x = 2 + log₃ y
y^x = 3⁸
y^x = 3⁸
xlog₃ y = 8*log₃ 3
x = 8/log₃ y
8/log₃ y = 2 + log₃ y
log₃² y + 2*log₃ y - 8 = 0
log₃ y = t
t² + 2t - 8 = 0
t₁ = - 4
t₂ = 2
log₃ y = - 4
y = 3⁻⁴
y₁ = 1/81
log₃ y = 2
y = 3²
y₂ = 9
x = 8/log₃ y
x = 8/ (-4)
x₁ = - 2
x₂ = 8/2
x₂ = 4
Ответ: (- 2; 1/81) (4 ; 9)
2/3 + 7/15 - 2а/12 = 2*20 / 60 + 7*4 / 60 - 2а*5 / 60 =
= 40+28-10а / 60 = 68-10а / 60 = 2(34-5а) / 2*30 = 34-5а / 30