
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
If a sequence $\{a_n\}$ satisfies $\dfrac{1}{{a_{n+1}}}-\dfrac{1}{{a_n}}=d$ (where $d$ is a constant), then the sequence $\{a_n\}$ is called a "harmonic sequence". Given that the sequence $\left\{ \dfrac{1}{{b_n}} \right\}$ is a "harmonic sequence" and $b_1+b_2+\cdots +b_9=90$, then $b_4+b_6=$ ______.

Present the answer in LaTex format: \boxed{Your answer}
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