<span>1 3/4 ч=7км, 105мин=7000м, 1 мин= х м, 105х=7000, 10,5х=700,
21/2х=700, х=700:21/2, х=200/3, 1 мин=200/3м, 2ч=х м, 2ч=120мин,
2ч=120*200/3, 2ч=8000м, 2ч=8км, 7км+10,5км+8км=25,5км, Турист от А
пункта через 2 часа находился в 25,5 км.</span>
Решение
<span>a</span>₂ <span>= a</span>₁ <span>+ d
</span><span>a₉ </span><span>=a₁ </span><span>+ </span><span>8d
</span><span>a</span>₂ <span>= 3a</span>₉
<span>3(a</span>₁ <span>+ 8d) = a</span>₁ <span>+ d
</span><span>3a</span>₁ <span>+ 24d = a</span>₁ <span>+ d
</span><span>2a</span>₁ <span>+ 23d = 0
</span><span>2a</span>₁ = - 23d
<span>a</span>₁ = - 11,5d
<span>Sn = [2a</span>₁ + d*(n - 1)*n]/2
S₂₀ = [(a₁ + a₁ + 19d)*20]/2 = (a₁ + a₂₀)*10
<span>
</span>
В₁=-4
В₆=1/8
В₆=В₁ * q⁵
1/8= -4 *q⁵
q⁵=1/8 : (-4)
q⁵= <u>-1 </u>
8*4
q⁵=<u> - 1 </u>
2³ * 2²
q⁵ = <u> -1 </u>
2⁵
q⁵ = (<u> -1 </u>)⁵
( 2 )
q=<u>-1 </u>
2
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