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lilihurry銀蟲(chóng) (小有名氣)
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[求助]
請(qǐng)大師幫忙解決一道二元二次方程組,急,謝謝! 已有2人參與
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| 解方程組 ①x2-y2-5x+y+8=0, ②2xy-x-5y+1=0 |
鐵蟲(chóng) (初入文壇)
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x^2 - y^2 - 5*x + y + 8 = 0 (1) 2*x*y - x- 5*y + 1 = 0 (2) (1): x^2 - 5x + (5/2)^2 - (y^2 + y + (1/2)^2) + 2 = 0 (x -5/2)^2 - (y - 1/2)^2 + 2 = 0 (2x - 5)^2 - (2y - 1)^2 + 8 = 0 (3) (2): y(2x - 5) = x - 1, y = (x - 1)/(2x - 5) (4) 2y - 1 = 3/(2x - 5) 令 2x - 5 = u 2y - 1 = 3/u 代入 (3) u^2 - 9/u^2 + 8 = 0 u^4 + 8u^2 - 9 = 0 (u^2 - 1)(u^2 + 9) = 0 u = 1, -1, 3i, -3i u = 2x - 5 = 1, x = 3, y = (3/u + 1)/2 = 2 u = 2x - 5 = -1, x = 2, y = (3/u + 1)/2 = -1 u = 2x - 5 = 3i, x = (5 + 3i)/2, y = (3/u + 1)/2 = (1 - i)/2 u = 2x - 5 = -3i, x = (5 - 3i)/2, y = (3/u + 1)/2 = (1 + i)/2 |
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銀蟲(chóng) (小有名氣)
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