When the pair of linear equations $kx+4y=5$,$3x+2y=5$ is consistent only?


Given:  Pair of linear equations: $kx+4y=5$,$3x+2y=5$

To do: To find the value of $k$ when given pair of equations is consistent only.

Solution:

A pair of linear equations is consistent if it has a solution either a unique or
infinitely many.

Given equations are:

$kx+4y=5         .....( 1)$

$3x+2y=5        ......( 2)$

Here, $a_1=k,\ b_1=4,\ c_1=−5$ and $a_2=3,\ b_2=2,\ c_2=−5$

For given system,

$\frac{a_1}{a_2}=\frac{k}{3}, \frac{b_1}{b_2}=\frac{4}{2}=2$ and $\frac{c_1}{c_2}=\frac{-5}{-5}=1$

Here $\frac{b_1}{b_2}\
eq \frac{c_1}{c_2}$

Hence, the system does not have infinitely many solution. So, the equations must have a unique solution.  

$\Rightarrow \frac{a_1}{a_2}\
eq\frac{b_1}{b_2}$

$\Rightarrow \frac{k}{3}\
eq2$

$\Rightarrow k\
eq6$
 

Thus, for $k\
eq6$, given pair of linear equations is consistent only.

Updated on: 10-Oct-2022

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