Question

for what value of K is 3 a root of the eqn. 2x^2+x+k=0​

Answer 1

Answer:

k=(-21)

Step-by-step explanation:

$p(x)=2x^{2} +x+k =0\\p(3)= 2(3)(3) +3+k=0\\18+3+k =0\\21+k=0\\k=(-21)$

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Answer 2

Answer:

k = -21

Step-by-step explanation:

Given a quadratic equation such that,

$2 {x}^{2} + x + k = 0$

Also, given that 3 is a root of the Equation.

To find the value of k,

We know that,

A root of an equation satisfies that Equation.

Therefore, we need to satisfy the given quadratic equation by 3 .

Substituting the values, we get,

$= > 2( {3}^{2} ) + 3 + k = 0 \\ \\ = > 2(9) + 3 + k = 0 \\ \\ = > 18 + 3 + k = 0 \\ \\ = > k + 21 = 0 \\ \\ = > k = - 21$

Hence, the required value of k = -21.