求助~~~~~~~中二聯立方程－wszspj2的部落格

標題:

求助~~~~~~~中二聯立方程

發問:

x+y=13------------------------(1) (10y-(13-y))-(10(13-y)+y=45-------------(2) 求xy 更新: x+y=7-----------------------(1) 10y+x+3=(10x+y)11------------------------(2) 更新 2: 求xy 順便替我做多1題

最佳解答:

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Q1) x + y = 13..................................................(1) (10y-(13-y)) - (10(13-y) + y) = 45.............(2) From eq(2): (10y-13+y) - ( 130 - 10y + y ) = 45 11y - 13 - 130 + 10y - y = 45 20y = 45 + 13 + 130 y = 188/20 y = 9.4 Sub y=9.4 into eq(1): x + 9.4 = 13 x = 3.6 Therefore, xy = 3.6 x 9.4 = 33.84 Q2) x + y = 7.................................(1) 10y + x + 3 = (10x+y)11.........(2) From eq(2): 10y + x + 3 = 110x + 11y 3 = 109x + y............................(3) eq(3) - eq(1): 108x = -4 x = -1/27 Sub x=-1/27 into eq(1): -1/27 + y = 7 y = 190/7 Therefore, xy = (190/7) x (-1/27) = -190/189

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