срочно. решите. нужно быстро

b1 = - 8

q = 1/2

b7 = b1*q^6 = - 8/64 = - 1/8

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b1 = 128

q = 1/4

b4 = b1*q^3 = 128/64 = 2

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b6 = b1*q^5 = 1/27

b1*(1/3)^5 = 1/27

b1 = 243/27

b1 = 9

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b5 = b1*q^4 = 11

b7 = b1*q^6 = 99

q^4/q^6 = 1/9

1/q^2 = 1/9

q^2 = 9

q = 3; q = - 3