(Ⅱ)由(Ⅰ)可知an=6-4n,求得Sn= n(2+6-4n) 2=4n-2n2.再由Sk=-48,可得4k-2k2=-48,解得k的值. 解答:解:(Ⅰ)设等差数列{an}的公差为d,则an=a1+(n-1)d.由a1=2,a3=-6,可得2+2d=-6,解得d=-4.从而,an=2+(n-1)×(-4)=6-4n.---(5分)(Ⅱ)由(Ⅰ)可知an=6-4n,所以Sn=...
A toner process comprising the aggregation and coalescence of an amorphous polyester, a crystalline polyester and a colorant, and wherein the coalescence is conducted at a temperature that is about lower than the melting point temperatur... K Zhou,GG Sacripante,KA Moffat,... - US 被引量: ...