Відповідь: А) 427
b1 = 7, b2 = -21
b2 = b1 × q²¯¹
q = b2 / b1 = -21 / 7 = -3
b3 = b1 × q³¯¹
b3 = 7 × (-3)² = 7 × 9 = 63
b4 = b1 × q⁴¯¹
b4 = 7 × (-3)³ = 7 × (-27) = -189
b5 = 7 × (-3)⁴ = 7 × 81 = 567
b1 + b2 + b3 + b4 + b5 = 7 + (-21) + 63 + (-189) + 567 = 427