[填空题]
The graphs of y=-0.5 x+2.5 anl (nsr.g+8sw qd -wdod c084/q1dlg :+x o zpihc $y=0.5 x^{2}+0.5 x+1$ intersect at (-3,4) and (1,2) , as shown in the following diagrams.
1. Calculate the shaded area in diagram 1 , the area enclosed by the lines y=-0.5 x+2.5 x=-3, x=1 and the x -axis, A$_1$= units$^2$
2. 1. Write down an integral for the shaded area in diagram 2 , the area enclosed by the curve y=$0.5 x^{2}+0.5 x+1$ , the lines x=-3 and x=1 , and the x -axis.
A$_2$=$\int_{-3}^{1}\left(0.5 x^{2}+0.5 x+a\right) \mathrm{d} x$;a= .
2. Calculate the area of this shaded region,A$_2$≈ units$^2$
3. Hence, determine the area enclosed by the line y=-0.5 x+2.5 and the curve y= $0.5 x^{2}+0.5 x+1$
