[Math] When to use the limit comparison test

calculusconvergence-divergencedivergent-series

$$\int_{7}^{\infty}\frac{1}{\sqrt{v-5}}$$ I tried using the limit comparison test and found that $\frac{1}{\sqrt{v}}\leq\frac{1}{\sqrt{v-5}}$ and therefore tried t find $\lim_{x\to\infty}\frac{\frac{1}{\sqrt{v}}}{\frac{1}{\sqrt{v-5}}}$ and found that it converges as the limit is 1 . However, the answer is diverge . Am i doing it right ?

Should i have used the Direct Comparison Test instead or could the answer also be solved by using the limit comparison test? because i'm not quite sure when to use which one

Best Answer

You were almost there. Indeed, you forgot the last step:

$$\int_7^\infty\frac1{\sqrt v}dv\to\infty$$

Thus, it diverges.

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