Question

Помогите пожалуйста, Срочно!!!!

Answer 1

1)

3x + 4y = 43  (* 7)

11x - 7y = 6  ( * 4)

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21x + 28y = 301   (+)

44x - 28y = 24     (+)

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21x + 28y = 301

65x = 325

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x = 5

105 + 28 y = 301

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x = 5

28 y = 196

--

x = 5

y = 7

2)

x + 2y = 25

xy = 11

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x = 25 - 2y

(25 - 2y) y = 11

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x = 25 - 2y

25y - 2 y ^ 2 = 11

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x = 25 - 2y

2 y^2 - 25y + 11 = 0    D = 625 - 88 = 537

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y = (25 +- sqrt(537)) / 4

x = 25 - 2y

=>

либо x = (25 - sqrt(537)) / 2  y = (25 + sqrt(537)) / 4

либо x = (25 + sqrt(537)) / 2 y = (25 - sqrt(537)) / 4