求1+2x^2+3x^4+...+10x^18的和知道使用错位相减,可是最后为什么是x^2(1-x^18)/1-x^2为什么是x^18不是x^9他们相加没有18项昂!

已知x=2π+1求 |x-1|+|x-2|+|x-3|+|x-4|+|x-5|+|x-6|+|x-7|+|x-8|+|x-9|+|x-10| 已知x=2π+1.求(X-1)+(X-2)+(X-3)+(X-4)+(X-5)+(X-6)+(X-7)+(X-8)+(X-9)+(X-10) x(x+1)+(x+2)+(x+3)+(x+4)+(x+5) = 27求x 求一个数独答案X X X 9 X X X 8 2 X 6 3 X X 1 4 X 99 X 8 X X X X X XX X X 6 7 X 3 X XX 4 6 X 5 X 2 9 XX X 7 X 2 3 X X XX X X X X X 7 X 17 X 4 3 X X 6 2 X6 3 X X X 7 X X X 一个“整式的乘法”的问题请先阅读下列解题过程,再仿做下面的问题.已知X*X + X - 1=0,求X*X*X + 2*X*X + 3的值.解X*X*X + 2X*X +3=X*X*X +X*X -X +X*X +X +3=X{X*X +X -1} +X*X +X -1 +4=0+0+4=4+ x + X*X + X*X*X=0.+ X*X + X*X*X 1X?+2X?+3X?+4X?+5X?+6X?+7X?+8X?+9X?+10X?=1980求?是多少 |x^2-4x+3|+|x+1|>8 求x *-----------------------------------------------*| 6 4 X | 8 X X | X X 5 || X X X | X X X | X 7 8 || X X X | X X X | X X X ||---------------+---------------+--------------- || X X X | X X X | 5 1 X || X X X | X 6 X | X X X || 8 X X | 3 5 X | 2 X X || f(x)=1/(x+1)(x+2)+1/(x+2)(x+3)+1/(x+3)(x+4)+.1/(x+9)(x+10) 求f(8) 已知x^-x-1=0,求x^4+x^3-x^2-4x+3 求|x-1|+|x-2|+|x-3|+|x-4|+|x-5|+...+|x-2007|的最小值 /x-1/+/x-2/+/x-3/x-4/+/x-5/ +/x-6/求最小值 (x-1)(x-2)(x-3)(x-4)=(x+5)(x+6)(x+7)求X等于几? 已知1+x+x^2+x^3=0,求x+x^2+x^3+x^4+x^+x^6+x^7+x^8的值 如果1+x+x^2+x^3=0,求x+x^2+X^3+x^4+x^5+x^6+x^7+x^8的值, 3^x=2^x,求x.5^(x-1)·10^3x=8^x求x 已知x^2-3x+1=0求x^4-5x^3+10x^2-11x+5 (x-1)/(x+3x+2)+6/(2+x-x)-(10-x)/(4-x)