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Ratling [72]
3 years ago
5

Solve x and y simultaneously if:

Mathematics
1 answer:
Solnce55 [7]3 years ago
5 0

Answer:

make Y the subject in eqn........ 1

y + 7 = 2x

y = 2x - 7...........eqn 3

put y = 2x - 7 into eqn 2

x² - xy + 3y² = 15

x² - x(2x - 7) + 3(2x - 7)(2x - 7) = 15

x² - 2x² + 7x + 3(4x² + 14x -14x + 21) = 15

x² - 2x² + 7x + 12x² + 42x - 42x + 63 = 15

x² - 2x² + 7x + 12x² + 63 = 15

x² - 2x² + 12x² + 7x + 63 = 15

11x² + 7x + 63 - 15 = 0

11x² + 7x + 48 = 0

11x² + 7x = - 48

11x²/11 + 7x/11 = - 48/11

x² + 7x

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At time, 10 seconds, the mass remaining is 24 grams

At time, 20 seconds, the mass remaining is 12 grams

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Step-by-step explanation:

Given;

initial mass of the radioactive element  = 48 grams

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time of decay (s)                          remaining mass of the  radioactive element

0 ------------------------------------------------- 48 grams

10------------------------------------------------- 24 grams

20 ------------------------------------------------- 12 grams

30 -------------------------------------------------- 6 grams

40 --------------------------------------------------- 3 grams

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