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F.2 (4條)急!!英文數 20點!!!

發問:

Solve the following simultaneous equations by the method of elimination. 1. { 2x + 3y = -1 3x + 2y = 1 2. { 3x = 5y - 9 5x = 3y + 1 3. { 2x - 9y = 20 5x + 4y = -3 4. { 5x + 11y = 43 -2x + 3y = 5 [ { ] 係連埋下面的. 要埋式，因為我吾明點做，所以請清楚地列出，十分感激!!!

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1. 2x + 3y = -1 ----------(1) 3x + 2y = 1 --------------(2) (2)*2/3 - (1), 4y/3 - 3y = 2/3 + 1 -5y/3=5/3 y = -1 Sub y = -1 into(1) 2x - 3 = -1 2x = 2 x = 1 2. 3x = 5y - 9 --------(1) 5x = 3y + 1 -----------(2) (2)*3/5 - (1), 0 = 9y/5 - 5y + 3/5 + 9 0 = 34y/5 + 48/5 y=-48/34 y=-24/17 Sub y= -24/17 into(1), 3x = 5(24/17) - 9 x = 40/17 - 51/17 x = -11/17 3. 2x - 9y = 20 -------(1) 5x + 4y = -3 ---------(2) (2)*2/5 - (1), 8y/5 + 9y = -6/5 - 20 53y/5 = -106/5 y = -2 Sub y = -2 into(1) 2x + 18 = 20 2x=2 x=1 4. 5x + 11y = 43 ----------(1) -2x + 3y = 5 ----------(2) (1)*2/5 + (2), 22y/5 + 3y = 86/5 + 5 37y/5 = 111/5 y=3 Sub y=3 into (1), 5x + 33 = 43 5x = 10 x =2

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