Question

方程组5/x+1+4/y-2=2 7/x+1+3/2-y=13/20

Answer 1

5/(x+1)+4/(y-2)=2 (1)

7/(x+1)+3/(2-y)=13/20

所以7/(x+1)-3/(y-2)=13/20 (2)

(1)*3+(2)*4

15/(x+1)+12/(y-2)+28/(x+1)+12/(y-2)=6+13/5

43/(x+1)=43/5

x+1=5,x=4

代入(1)

5/5+4/(y-2)=2,4/(y-2)=-1,y-2=-4,y=-2

所以x=4,y=-2

设百位是x,个位是y

则这个数是100x+y

他的数字和=x+y

所以100x+y=67(x+y)

33x-66y=0

x-2y=0

x=2y

交换后是100y+x

数字和=x+y

所以m=(100y+x)/(x+y)

因为x=2y

所以m=(100y+2y)/(2y+y)=102y/3y=34