(1)2x-3=5-x
x=8/3
代入Y1
y=7/3
(2)2x-3>5-x
x>8/3
(3)A(8/3,7/3) B(3/2,0) C(5,0)
BC=7/2 H=7/3
S=1/2*7/2*7/3=49/12