Question

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Answer 1

Răspuns:

Explicație pas cu pas:

1.

b2 = b1*q

20 = 4*q

q = 20 : 4 = 5

b3 = b2*q = 20*5 = 100

b4 = b3*q = 100*5 = 500

2.

b1 = -1/2

b2 = b1*q

b3 = b1*q^2

b4 = b1*q^3

(-1/2)*q^3 = -4

q^3 = -4 : (-1/2) = 8 = 2^3

q = 2

b1 = -1/2

b2 = -1/2*2 = -1

b3 = -1*2 = -2

b4 = -2*2 = -4

b5 = -4*2 = -8

b6 = -8*2 = -16

b7 = -16*2 = -32

b8 = -32*2 = -64

S8 = -1/2 - 1 -2 -4 - 8 - 16 - 32 - 64 = -1/2 - 127 = -127,5

______________________

b5 = -7250

q = 5

b5 = b1*q^4

-7250 = b1*5^4 = b1*625

b1 = -7250 : 625 = -11,6

b10/b7 = b1*q^9/b1*q^6 = q^3 = 5^3 = 125

________________________

q = 2

S5 = b1 + b2 + b3 + b4 + b5

= b1 + b1*q + b1*q^2 + b1*q^3 + b1*q^4

= b1*(1 + q + q^2 + q^3 + q^4)

31√3 = b1*(1 + 2 + 4 + 8 + 16) = b1*31

b1 = 31√3 : 31 = √3

b7 = b1*q^6 = √3 * 2^6 = 64√3

b1 + b2 = √3 + 2√3 = 3√3