(1)∵交点为(1, 3)
∴将(1, 3)代入y=0.25x+b1得
3=0.25+b1
b1=2.75(即11/4)
将(1, 3)代入y=kx+b2得
3=k+b2
b2=3-k
∴y2=kx+3-k
又∵y2过(4,0).代入y2=kx+3-k得
0=4k+3-k
k=-1
∴b2=3-k=4
∴y1=1/4x+11/4,y2=-x+4
(2)y=1/4x+11/4交x轴与(-11,0)
y=-x+4交x轴于(4,0)
y=1/4x+11/4交y=-x+4于(1,3)
S△=0.5×15×3=22.5