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.
问题描述：
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.
答
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