题目

Through a series of experiments an American scientist has gained an understanding of the social structure of the most complex of ant societies. The ants examined are the only creatures other than man to have given up hunting and collecting for a completely agricultural way of life. In their underground nests they plant gardens on soils made from finely cut leaves. This is a complex operation requiring considerable division of labor. The workers of this type of ant can be divided into four groups according to size. Each of the groups performs a particular set of jobs.    The making and care已知二次函数y=ax2+bx+c的图象与x轴交于点（-2，0）、（x1，0），且1＜x1＜2，与y轴的正半轴的交点在（0，2）的下方．下列结论：①4a-2b+c=0；②a＜b＜0；③2a+c＞0；④2a-b+1＞0．其中正确结论的个数是    个．