如图,过点B(4,2)分别作x轴,y轴垂线,垂足分别为点C,A.反比例函数y=k/x的图像经

(1)
A(0,2),B(4,2),M(2,2)
y = k/x,2 = k/2,k = 4
y = 4/x
取x = 4,y = 4/4 = 1,N(4,1)
C(4,0),B(4,2),BC的中点(4,1),N是BC的中点
(2)
四边形OMBN的面积 = 梯形ACBM的面积 - 三角形ACN的面积
= (1/2)(MB + OC)*CB - (1/2)*OC*CN
= (1/2)(2 + 4)*2 - (1/2)*4*1
= 4
(3)
B(u,v),M(u/2,v),N(u,v/2)
四边形OMBN的面积 = 梯形ACBM的面积 - 三角形ACN的面积
= (1/2)(MB + OC)*CB - (1/2)*OC*CN
= (1/2)(u/2 + u)*v - (1/2)u*(v/2)
= 3uv/4 - uv/4
= uv/2 = a
y = k/x
k = xy = (u/2)*v = uv/2 = a
y = a/x