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f2數-solve simultaneous equations
1)a man is 22 years older than his son.In 2 years' time his age plus half his son's age will be 55 years.How old is he now?2)a man is 20 years older than his son.In 4 years' time he will be twice as old as his son.find his present age.3)four years ago a man was 12 times as his son.their... 顯示更多 1)a man is 22 years older than his son.In 2 years' time his age plus half his son's age will be 55 years.How old is he now? 2)a man is 20 years older than his son.In 4 years' time he will be twice as old as his son.find his present age. 3)four years ago a man was 12 times as his son.their united ages at present total 47 years.how old is the son now? *英文步驟 **[最好]有中文解釋
最佳解答:
1) let the present's age of a man and his son be x & y, x-y=22 ---(1) (x+2)+ (y+2)/2 =55 => 2x+y=104 ---(2) (1)+(2): 3x=126 x=42, y=20 Therefore, the present's age of a man is 42 yrs old. 2) let the present's age of a man and his son be x & y, x-y=20 ---(1) (x+4) = 2(y+4) => x-2y=4 ---(2) (1)-(2): y=16, x=36 Therefore, the present's age of a man is 36 yrs old. 3) let the present's age of a man and his son be x & y, (x-4) = 12(y-4) => x-12y= -44 ---(1) x+y=47 ---(2) (2)-(1): 13y=91 y=7, x=40 Therefore, the present's age of his son is 7 yrs old. 2008-02-20 20:46:35 補充： 中文解釋如下1) 列式(1)：爸現在年齡與比仔差22年；列式(2)：2年后，爸年齡加仔年齡一半共55歲。2) 列式(1)：爸現在年齡與比仔差20年；列式(2)：4年后，爸年齡係仔年齡2倍。3) 列式(1)：4年前，爸年齡係仔年齡12倍；列式(2)：爸現在年齡加仔年齡共47歲。
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f2數-solve simultaneous equations
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發問:1)a man is 22 years older than his son.In 2 years' time his age plus half his son's age will be 55 years.How old is he now?2)a man is 20 years older than his son.In 4 years' time he will be twice as old as his son.find his present age.3)four years ago a man was 12 times as his son.their... 顯示更多 1)a man is 22 years older than his son.In 2 years' time his age plus half his son's age will be 55 years.How old is he now? 2)a man is 20 years older than his son.In 4 years' time he will be twice as old as his son.find his present age. 3)four years ago a man was 12 times as his son.their united ages at present total 47 years.how old is the son now? *英文步驟 **[最好]有中文解釋
最佳解答:
1) let the present's age of a man and his son be x & y, x-y=22 ---(1) (x+2)+ (y+2)/2 =55 => 2x+y=104 ---(2) (1)+(2): 3x=126 x=42, y=20 Therefore, the present's age of a man is 42 yrs old. 2) let the present's age of a man and his son be x & y, x-y=20 ---(1) (x+4) = 2(y+4) => x-2y=4 ---(2) (1)-(2): y=16, x=36 Therefore, the present's age of a man is 36 yrs old. 3) let the present's age of a man and his son be x & y, (x-4) = 12(y-4) => x-12y= -44 ---(1) x+y=47 ---(2) (2)-(1): 13y=91 y=7, x=40 Therefore, the present's age of his son is 7 yrs old. 2008-02-20 20:46:35 補充： 中文解釋如下1) 列式(1)：爸現在年齡與比仔差22年；列式(2)：2年后，爸年齡加仔年齡一半共55歲。2) 列式(1)：爸現在年齡與比仔差20年；列式(2)：4年后，爸年齡係仔年齡2倍。3) 列式(1)：4年前，爸年齡係仔年齡12倍；列式(2)：爸現在年齡加仔年齡共47歲。
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