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If the system of equations x − y = 2mx + y = 6 has a nonnegative integer solution, then the positive integer m is () A. 0，1B. 1，3，7C. 0，1，3D. 1，3
X − y = 2, ① MX + y = 6, ②, ① + ②, (M + 1) x = 8, the solution is x = 8m + 1, substituting x = 8m + 1 into ①, 8m + 1-y = 2, the solution is y = 6 − 2mm + 1, ∵ the solution of the system of equations is a non negative integer, ∵ 8m + 1 ＞ 0, ① 6 − 2mm + 1 ≥ 0, ②, the solution of inequality ①, m ＞ - 1, the solution of inequality ②, m ≤ 3, so, - 1 ＜ M
Equation: 12|3600 × (x-4.5) = 16.5|3600 × (x-18)
"|" is a division sign
12/3600*(x-4.5)=16.5/3600*(x-18) 12*(x-4.5)=16.5*(x-18) 12x-12*4.5=16.5x-16.5*18 4.5x=16.5*18-12*4.5 4.5x=297-54 4.5x=243 x=54
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