Вопрос школьника по предмету Алгебра
(x2-6x-9)^2=x(x^2-4x-9)
Ответ учителя по предмету Алгебра
(x^2 — 6x — 9)^2 — x(x^2 — 4x — 9) = 0 /:x^2 ≠ 0
(x — 6 — 9/x)^2 — (x — 4 — 9/x) = 0
Пусть x — 6 — 9/x = y, тогда
y^2 — (y + 2) = 0
y^2 — y — 2 = 0
D = 1 + 4*2 = 9
y1 =( 1 + 3)/2 = 4/2 = 2
y2 = (1 — 3 )/2 = — 2/2 = -1
1) x — 6 — 9/x = 2
x — 6 — 9/x — 2 = 0
x — 8 — 9/x = 0
x^2 — 8x — 9 = 0
D = 64 + 36 = 100
x1 = (8 + 10)/2 = 18/2 = 9
x2 = (8 — 10)/2 = — 2/2 = — 1
2) x — 6 — 9/x = — 1
x — 5 — 9/x = 0
x^2 — 5x — 9 = 0
D = 25 + 36 = 61
x3 = ( 5 + √61)/2 = 2,5 + √61/2
x4 = (5 — √61)/2 = 2,5 — √61/2
Ответ
— 1
9
2,5 — √61/2
2,5 + √61/2
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