Ответ:
1.
а) (a - 3b)(c + d) = ac + ad - 3bc - 3bd
б) (2b + c)(3a - 1) = 6ab - 2b + 3ac - c
в) (2c - 3)(3d - 5) = 6cd - 10c - 9d + 15
г) (c² + 1)(c - 7) = c³ - 7c² + c - 7
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2.
а) (a - 3)(3a + 1) = 3a² + a - 9a - 3 = 3a² - 8a - 3
б) (2b + 2c)(3b + 5c) = 6b² + 10bc + 6bc + 10c² = 6b² + 16bc + 10c²
в) (2c² - 3)(3 - 5c²) = 6c² - 10c⁴ - 9 + 15c² = 21c² - 10c⁴ - 9
г) (3c + ab)(3c - ab) = 9c² - a²b² ⇒ по формуле (a + b)(a - b) = a² - b²
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Answers & Comments
Ответ:
1.
а) (a - 3b)(c + d) = ac + ad - 3bc - 3bd
б) (2b + c)(3a - 1) = 6ab - 2b + 3ac - c
в) (2c - 3)(3d - 5) = 6cd - 10c - 9d + 15
г) (c² + 1)(c - 7) = c³ - 7c² + c - 7
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2.
а) (a - 3)(3a + 1) = 3a² + a - 9a - 3 = 3a² - 8a - 3
б) (2b + 2c)(3b + 5c) = 6b² + 10bc + 6bc + 10c² = 6b² + 16bc + 10c²
в) (2c² - 3)(3 - 5c²) = 6c² - 10c⁴ - 9 + 15c² = 21c² - 10c⁴ - 9
г) (3c + ab)(3c - ab) = 9c² - a²b² ⇒ по формуле (a + b)(a - b) = a² - b²