Question

Which of the following is the value of k if oneday root of the quadratic eqution x2+kx-8=0 is -4​

Answer 1

Answer:

k=4

Step-by-step explanation:

-4 is the root of quadratic equation 2x+kx-8=0

therefore, -4 will be the solution of given equation

now,

2x-kx-8=0

put -4 in place of x

2(-4)-k(-4)-8=0

-8+4k-8=0

4k-16=0

4k=16

k= 4

hope it will help you.

Answer 2

$\large \bf \green {⚝ \: Question \: ࿐}$

Which of the follow is the value of $\sf k$ if one of the root of the quadratic equation $\sf x^2+kx-8=0$ is $\sf -4$?

$\large \bf \green {⚝ \: Solution\: ࿐}$

It is given that -4 is one of the root of the equation.

We have to find the value of k :-

Substituting x = -4 in the equation and solving :-

$\red {: \: \longmapsto} \: \sf x^2+kx - 8 = 0$

$\red {:~\longmapsto}~\sf (-4)^2+k(-4) - 8 = 0$

$\red {:~\longmapsto}~\sf 16 - 4k - 8= 0$

$\red {:~\longmapsto}~\sf 8-4k=0$

$\red {:~\longmapsto }~\sf -4k=-8$

$\red {:~\longmapsto}~\sf k=\cfrac{-8}{-4}$

$\red {:~\longmapsto}~\sf k=2$

$\underline {\boxed {\rm \red {\therefore \: k=2 \: for \:x^2+kx-8 \: when \: -4 \: is \: one \: of \: the \: zero.}}}$

$\large \bf \green {⚝ \: Verification \: ࿐}$

Substituting x = -4 and k = 2 in the equation and solving :-

$\red {:~\longmapsto}~\sf x^2+kx-8=0$

$\red {: \: \longmapsto}\:\sf (-4)^2+(2)(-4)-8=0$

$\red {:\:\longmapsto} \: \sf 16 - 8 - 8 = 0$

$\red {:~\longmapsto}\:\sf 16-16=0$

$\red {:~\longmapsto}\:\sf 0=0$

$\underline {\boxed {\rm \red{Hence, \: verified \: !}}}$

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@Sita05࿐