Question

What is the value of K, so that x=3, is a solution of the equation Kx + 20 = 5x – 7​

Answer 1

$\huge\colorbox{red}{Answer}$

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Given:-

x = 3

Proof:-

$\sf{⇒ \: K(3) + 20 = 5(3) - 7}$

$\sf{⇒ \: 3K + 20 = 15 - 7}$

$\sf{⇒ \: 3K = 8 - 20}$

$\sf{⇒ \: 3K = - 12}$

$\sf{⇒ \: K = \frac{ - 12}{3}}$

$\large\sf\fbox{\color{navy}{⇒}{\color{yellow}{K = - 4}}}$

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$\huge{\underline{\underline{\color{pink}{Be\: brainly}}}}$

Answer 2

What we have to do ?

We know, that if x = 3 is solution , then we will plug the value of " x " simply in order to get the value of k.

Let's solve it :

Putting x = 3 in the required Equation -

$:\implies\sf Kx + 20 = 5x – 7$

$:\implies\sf (3)k + 20 = 5(3) - 7$

$:\implies\sf 3k + 20 = 15 - 7$

$:\implies\sf 3k + 20 = 8$

$:\implies\sf 3k = 8 - 20$

$:\implies\sf 3k = - 12$

$:\implies\sf k = \dfrac{-12}{3}$

$:\implies\sf k = - 4$

$\dashrightarrow\:\: \underline{ \boxed{\sf k = - 4}}$

$\underline{\sf{Verification}}$

Putting k = ( - 4 )

$\dashrightarrow\:\: \sf (3)(-4) + 20 = 5(3) - 7$

$\dashrightarrow\:\: \sf - 12 + 20 = 15 - 7$

$\dashrightarrow\:\: \sf 8 = 8$

L.H.S = R.H.S.

Hence , Verified !!