Сумма первых трех: b1*(q^3 - 1)/(q - 1) = 112
Сумма последних трех: b4*(q^3 - 1)/(q - 1) = -14
(q^3 - 1)/(q - 1) = 112/b1
(q^3 - 1)/(q - 1) = -14/b4
112/b1 = -14/b4
b1 = -8b4
b4 = b1*q^3 = -8b4*q^3, -8q^3 = 1, q = -1/2
(-1/8 - 1)/(-1/2 - 1) = 112/b1
b1 = 448/3
S5 = b1*(q^4 - 1)/(q - 1) = 448*(1/16 - 1)/3*(-1/2 - 1) = 448*15*2/3*16*3 = 56/3
V=пи*r^2*h;
h=V/пи*r^2;
d=1 => r=1/2;
h=пи/пи (1/2)^2;
h=4.
Y=2/3 x
4x-5(2/3 x)=8
4x-10/3 x=8
2/3 x=8
2x=24
x=12
y=2/3 от 12
у=8
ответ:
х=12
у=8