作业帮解题,联立二元一次方程 代入消元法和加减消元法都行.要完整列式
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解题,联立二元一次方程 代入消元法和加减消元法都行.要完整列式
Three years ago.the father's age was 8 times the son's age.Two years later,the father's age wii be 4.5 times the son's age.Find the present ages of the father and the son.
Three years ago.the father's age was 8 times the son's age.Two years later,the father's age wii be 4.5 times the son's age.Find the present ages of the father and the son.
设父亲年龄x,儿子年龄y
则：x-3=8*(y-3)
x+2=4.5*(y+2)
即：x=8y-24+3.1式
x+2=4.5y+9.2式
将1式代入2式得：
（8y-24+3）+2=4.5y+9
解得：y=8
将y=8代入1式得：
x=8y-24+3
x=43
则：x-3=8*(y-3)
x+2=4.5*(y+2)
即：x=8y-24+3.1式
x+2=4.5y+9.2式
将1式代入2式得：
（8y-24+3）+2=4.5y+9
解得：y=8
将y=8代入1式得：
x=8y-24+3
x=43