$a) 2n+7 ∈ B(n-3)$
$⇔ 2n+7=2(n-3)+13$
Để $2n+7 ∈ B(n-3)$
$⇔ 13 ∈ B(n-3)$
$⇒ n-3 ∈ ${$1,-1,13,-13$}
Ta có bảng giá trị:
\begin{array}{|c|c|}\hline n-3&1&-1&13&-13\\\hline n&4&2&16&-10 \\\hline\end{array}
$⇒ n ∈$ {$4,2,16,-10$}
$b) |x-2013|+(y-2014)^2$
$|x-2013|>0, (y-2014)^2>0$
Để $|x-2013|+(y-2014)^2=0$
$⇔ x-2013=0$
$⇔ x=2013$
$⇔ y-2014=0$
$⇔ y=2014$