S△OAC=1/2*OC*2/a(這步應(yīng)該懂吧)
=1/2*[b+(b-a)/(m-1)]*2/a
(A到B橫坐標距離為b-a,因為AB:BC=(M-1):1,所以B到C橫坐標距離為(b-a)/(m-1)再加上O到B橫坐標距離b即OC=b+(b-a)/(m-1))
=1/2*2/a*[b+(b-a)/(m-1)]
=1/a*[b+(b-a)/(m-1)]
=b/a+(b-a)/a*(m-1)
=b/a+b/a*(m-1)-a/a*(m-1)
=b/a+b/a*1/(m-1)-1/(m-1)
( 2/b:2/a=1/m所以應(yīng)該是a/b=m)
=m+m/(m-1)-1/m-1
=m+m-1/m-1
=m+1