Question

已知Y=Y1+Y2,其中Y1与X-1成正比例,Y2与X+1成反比例;且x=2时与x=3时,y的值都等于19.则y与x之间

Answer 1

Y1与X-1成正比例,设y1=a(x-1)

Y2与X+1成反比例,设y2=b/(x+1)

Y=Y1+Y2=a(x-1)+b/(x+1)

x=2时,

y=a(2-1)+b/(2+1)

=a+b/3=19-------------(1)

x=3时,

y=a(3-1)+b/(3+1)

=2a+b/4=19-----------(2)

由(2)-(1)×2得

-5b/12=-19,解得b=228/5;

将b=228/5带入(1),解得a=19/5.

所以y=19(x-1)/5+228/[5(x+1)]

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