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If One Root the Equation 2x2 + Kx + 4 = 0 is 2, Then the Other Root is - CBSE Class 10 - Mathematics

ConceptSolutions of Quadratic Equations by Factorization

Question

If one root the equation 2x2 + kx + 4 = 0 is 2, then the other root is

• 6

• -6

• -1

• 1

Solution

Let alpha and beta be the roots of quadratic equation2x^2 + kx + 4 = 0 in such a way that alpha = 2

Here, a  = 2, b = k and , c = 4

Then , according to question sum of the roots

alpha + beta = (-b)/a

2+ beta = (-k)/2

beta = (-k)/2 - 2

beta = (-k -4)/2

And the product of the roots

alpha .beta = c /a

= 4/2

= 2

Putting the value of beta = (-k -4)/2in above

2 xx (-k - 4)/ 2 = 2

(-k - 4) = 2

 k = -4 -2

= -6

Putting the value of in beta = (-k - 4)/2

beta = (-(6) - 4)/2

= (6-4)/2

 = 2/2

beta = 1

Therefore, value of other root be beta = 1

Is there an error in this question or solution?

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Solution If One Root the Equation 2x2 + Kx + 4 = 0 is 2, Then the Other Root is Concept: Solutions of Quadratic Equations by Factorization.
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