(v) x + 18 = 2y; y = 2x – 9
Sol. x + 18 = 2y
∴ x – 2y = – 18
y = 2x – 9
∴ – 2x + y = – 9
Changing the sign,
∴ 2x – y = 9
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D
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=
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1
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-2
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=
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(1 × -1) – (2 × -2)
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=
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-1 + 4
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=
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3
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2
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-1
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DX
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=
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-18
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-2
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=
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(-18 × -1) – (9 × -2)
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=
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18 + 18
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=
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36
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9
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-1
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DY
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=
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1
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-18
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=
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(1 × 9) – (2 × -18)
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=
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9 + 36
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=
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45
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2
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9
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By Cramer's rule,
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x
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=
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Dx
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=
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36
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=
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12
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D
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3
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y
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=
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Dy
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=
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45
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=
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15
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D
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3
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∴ x = 12 and y = 15 is the solution of given
simultaneous equations.
