2X + Y = 4
X - 3Y = - 5
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X = 3Y - 5
2X = 6Y - 10
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2X + Y = 4
2X = 4 - Y
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6Y - 10 = 4 - Y
7Y = 14
Y = 2
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X = 3 * 2 - 5 = 6 - 5 = 1
ОТВЕТ ( 1 ; 2 )
=======================
2X + 5Y = 15
X - 2Y = 3
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X = 2Y + 3
2 * ( 2Y + 3) + 5Y = 15
4Y + 6 + 5Y = 15
9Y = 9
Y = 1
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X = 2 + 3 = 5
ОТВЕТ ( 5 ; 1 )
=========================
5X - 10Y = 15
2X - 4Y = 6
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2X = 6 + 4Y
X = 3 + 2Y
2 * ( 3 + 2Y) - 4Y = 6
6 + 4Y - 4Y = 6
6 = 6
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4Y = 2X - 6
Y = 0,5X - 1,5
5X - 10*( 0,5X - 1,5) = 15
5X - 5X + 15 = 15
15 = 15
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ОТВЕТ любые значения переменных Х и Y