将一张矩形纸片折叠成如图所示的图形，若AB=6cm，则AC=____cm．

已知关于x的不等式ax²+bx+c＞0的解集为{x|﹣1＜x＜2}，求不等式a（x²+1）+b（x﹣1）+c＞2ax的解集．

填上“＜”、“＞”或“＝”．

如图所示是一个双量程电压表，表头是一个内阻R_g="500" Ω，满刻度电流为I_g="1" mA的毫安表，现接成量程分别为10 V和100 V的两个量程，则所串联的电阻R₁和R₂分别为

---Now more and more Chinese senior students are applying for admission to American universities through SAT.
---________. But taking an SAT may cost one more than 10,000 yuan.