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## Homework Statement

Show that if:

[tex]lim_{k\to\infty}b_k\to+\infty[/tex],

[tex]\sum_{k=1}^\infty a_k[/tex] converges and,

[tex]\sum_{k=1}^\infty a_k b_k[/tex] converges, then

[tex]lim_{m\to\infty} b_m \sum_{k=m}^\infty a_k = 0[/tex]

## Homework Equations

## The Attempt at a Solution

I only have an idea why this is true--[tex]\sum a_k[/tex] converges, so the tails become small, and [tex]\sum a_k b_k[/tex] converges, so [tex]a_k[/tex] shrinking dominates [tex]b_k[/tex] blowing up. I know that [tex]|b_k| < \epsilon / |a_k|[/tex] for any epsilon and large

*k*, and I know that [tex]\left| \sum_{m=k}^\infty a_m \right| < \epsilon[/tex] for large

*k*, but I can't find the way to combine these two statements.