lim[1/(1x4)+1/(4x7)+1/(7x10)+...+1/(3n-2)x(3n+1)]=_____
lim[1/(1x4)+1/(4x7)+1/(7x10)+...+1/(3n-2)x(3n+1)]=_____
100x( 3/1x4 + 3/4x7 +3/7x10 +.3/97x100)=?注:1x4、4x7、7x10等均为分母
是否存在常数C,使得等式1x4+2x7+3x10+.+n(3n+1)=n(n+c)(n+2c+1)对任意正整数n恒成立?
求和:1/1x4+1/4x7+···+1/(3n-2)x(3n+1)
3/(1X4)+3/(4X7)+3/(7X10)+3/(10X13)+3/(13X16)
已知数列1/1x4,1/4x7,1/7x10……1/(3n-2)(3n+1),又因为有一个运算技巧1/a1a2+1/a2
计算①1x2/1+2x3/1+3x4/1+```+19x20/1= ②1x4/1+4x7/1+7x10/1+```+91
1/1X4+1/4X7+1/7X10+...+1/100X103=
1/1X4+1/4X7+1/7X10+.+1/2002X2005=?
1X4/1+4X7/1+7X10/1+…+2005X2008/1=?
已知:x1=1/2+1/3,x2=1/3+1/4,x3=x2+x1,x4=x3+x2.,x10=x9+x8,求:x7/x
1x4分之一加4x7分之一加到(3n-2)x(3n+1)分之一等于多少