改正如下:
① x ⁴ - 6 x ² + 5 = 0
解:x ⁴ + (- 5 - 1)x ² + (- 5)(- 1)= 0
(x ² - 5)(x ² - 1)= 0
x ² - 5 = 0 或 x ² - 1 = 0
x1 = ± √5 x2 = ± 1
② x² + (√2 + √3)x + √6 = 0
解:x ² +(√2 + √3)x + √2 × √3 = 0
(x + √2)(x + √3)= 0
x + √2 = 0 或 x + √3 = 0
x1 = - √2 x2 = - √3
③ (2 x - 1)² = 9 (1 - 2 x)
解:(2 x - 1)² = - 9(2 x - 1)
(2 x - 1)² + 9(2 x - 1)= 0
(2 x - 1)(2 x - 1 + 9)= 0
(2 x - 1)(2 x + 8)= 0
2 x - 1 = 0 或 2 x + 8 = 0
x1 = 1 / 2 x2 = - 4
④ x ² - 2 a x + a ² - b ² = 0
解:(x ² - 2 a x + a ²)- b ² = 0
(x - a)² - b ² = 0
(x - a + b)(x - a - b)= 0
x - a + b = 0 或 x - a - b = 0
x1 = a - b x2 = a + b
参考公式:
十字相乘法:x ² + (p + q)x + p q = (x + p)(x + q)
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