问题
填空题
设数列{an}的通项为an=2n-10(n∈N+),则|a1|+|a2|+…+|a15|=______.
答案
∵an=2n-10,∴数列{an}是以2为公差,-8为首项的等差数列,
∴当1≤n≤5时,an,≤0;当n>5时,an>0,
则|a1|+|a2|+…+|a15|=-(a1+a2+…+a5)+(a6+a7+…+a15)
=-2(a1+a2+…+a5)+(a1+a2+…+a5)
=-2×
+5×(-8+0) 2
=13015×(-8+20) 2
故答案为:130.