[填空题]
Let $u_n$ = 5n - 1, for n∈$Z^+$.
1.1.Using sigma notation, write down an expression for $u_1$+$u_2$+$u_3$+...+$u_{10}$.
$u_1$+$u_2$+$u_3$+...+$u_{10}$=$\sum_{k=1}^10(u_k)$,$u_k$= -1
1.2.Find the value of the sum from part (a) (i).
the value of the sum= .
A geometric sequence is defined by $v_n$=5×2$^{n-1}$,for n∈$Z^+$.
2.Find the value of the sum of the geometric series $\sum_{k=1}^6(v_k)$.
the sum of 6 terms formula,we get $S_6$= .
