Question

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one root of the quadratic equation 2x2 +kx+4=0 is -2 then the value of k is​

Answer 1

$\large\bf\underline\red{Answer \: :- }$

$⟼\sf\pink{k = 6}$

$\large\bf\underline\red{Explanation \: :- }$

We have,

Quadratic equation = 2x² + kx + 4 = 0

x = -2

We have to find = k

Put the one root of quadratic equation -2 in 2x² + kx + 4 = 0.

$⟼\sf{2( - 2) {}^{2} + k( - 2) + 4 = 0} \\ ⟼\sf{2(4) + k( - 2) + 4 = 0 \: \: \: \: \: } \\ ⟼\sf{8 + 4 + ( - 2k) = 0} \: \: \: \: \: \: \: \: \: \: \: \\ ⟼\sf{12 + ( - 2k) = 0} \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \\ ⟼\sf{ - 2k = - 12} \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \\ ⟼\sf{k = \frac{ - 12}{ - 2} = \frac{12}{2} = 6} \: \: \: \: \: \: \: \\ ⟼\sf\pink{k = 6} \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \:$

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