6-15x=5x+112
6-112=5x+15x
-106=20x
x=-106/20
x=-5,3
A) √x - 9 = 0
√x =9
x=81
b) 1/2x² = 0
x² = 0
x = 0
-0,5; 1; - 2
b1 = -0.5
b2 = 1
q = b2/b1 = -2
Sn = b1(q^n - 1)(q - 1)
n = 4
S4 = -0.5 · ((-2)^4 - 1)/(-2 -1) = 2.5
Ответ: 2.5
На фото.................................................................
Х² - 6х - 7 = 0
D = 36 - 4 × 1 × (-7) = 36 + 28 = 64 > 0. 8.
х1 = 6 + 8 / 2 = 14/2 = 7.
х2 = 6 - 8 / 2 = -2/2 = -1.
Ответ : -1 ; 7.
Формула дискриминанта :
D = b² - 4 × a × c.
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