If one root of $5x^{2}+13x+k=0$ is the reciprocal of the other root, then find the value of $k$.


Given: One root of $5x^{2}+13x+k=0$ is the reciprocal of the other root.

To do: To find the value of $k$.

Solution:
 Let $\alpha$ is one root of the given polynomial.


It is given that other zero is Reciprocal the one zero.

So,
Other zero$=\frac{1}{\alpha}$.

Given polynomial is $5x^{2}+13x+k=0$.

Here,

coefficient of $( x^{2})=A=5$
 
coefficient of $( x)=B=x$

And, constant term $=C=k$.

Product of zeroes $=\frac{C}{A}$

$\alpha\times\frac{1}{\alpha}=\frac{k}{5}$

$1=\frac{k}{5}$

$k=5$

Then,  $k=5$.

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Updated on: 10-Oct-2022

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