## Precalculus (6th Edition) Blitzer

$-5260$
We are given that the sequence $a_n$ is an arithmetic sequence and the sequence $b_n$ is a geometric sequence. Here, we have $r=-2$ and $d=-15$ The general formula to find the nth term of a Geometric sequence is given as: $a_{n}=a_1r^{n-1}$ Thus, $a_{11}=a_1r^{11-1} =(-5)(-2)^{10} =-5120$ The general formula to find the nth term of an arithmetic sequence is given as: $a_{n}=a_1+(n-1) d$ and $b_{11}=10+(11-1) (-15) =10-150=-140$ Now, $a_{11}+b_{11}=-5120-140=-5260$