Предмет: Алгебра, автор: catyasofronowa

1.сколько отрицательных членов содержит арифметическая прогрессия -20 ; -19,2 ;-18,4 ;...?
а)18
б)20
в)25
4)30

2.( x^{2} -9) \sqrt{x}-2 =0

Ответы

Автор ответа: Аноним
4
1) а1 = -20
d=-19,2 + 20 = 0,8
an < 0
an = -20 +0,8(n - 1)
-20 + 0,8(n - 1) < 0
-20 + 0,8 n - 0,8<0
0,8 n< 20,8
n< 26
Ответ: 25

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