18.观察下列各式
(x-1)(x+1)=x2-1
(x-1)(x2+x+1)=x3-1
(x-1)(x3+x2+x+1)=x4-1
根据规律可得(x-1)(xn-1+…+x+1)=xn-1(其中n为正整数)
(x-1)(x+1)=x2-1
(x-1)(x2+x+1)=x3-1
(x-1)(x3+x2+x+1)=x4-1
根据规律可得(x-1)(xn-1+…+x+1)=xn-1(其中n为正整数)
12.已知下列各数a2+1,a2-1,a2,|a|,a,其中一定不是负数的有( )
| A. | 1个 | B. | 2个 | C. | 3个 | D. | 4个 |
10.下列算式中,结果为正数的是( )
| A. | -2×5 | B. | -6÷(-2) | C. | 0×(-1) | D. | 5÷(-2) |
9.
如图,在平面直角坐标系xOy中,?OABC的边OC在x轴上,A(1,4)、C(3,0)点D在AB上,D(3,4),过点D的直线l平分?OABC的面积,现将l绕点A逆时针旋转90°得直线l′,则直线l′的函数解析式为( )
0 294894 294902 294908 294912 294918 294920 294924 294930 294932 294938 294944 294948 294950 294954 294960 294962 294968 294972 294974 294978 294980 294984 294986 294988 294989 294990 294992 294993 294994 294996 294998 295002 295004 295008 295010 295014 295020 295022 295028 295032 295034 295038 295044 295050 295052 295058 295062 295064 295070 295074 295080 295088 366461
| A. | y=-2x+6 | B. | y=-2x+6.5 | C. | $y=-\frac{1}{2}x+\frac{5}{2}$ | D. | $y=-\frac{1}{2}x+\frac{13}{2}$ |