Question Details

One root of the quadratic equation 2x2+(k+3)x+2k=0 is reciprocal of the other. Find the roots.

Options

A

1/2 and 2

B

1 and 1

C

-1 and -1

D

-1 and 1

Show Answer

Correct Answer :

Option C

-1 and -1

Solution :

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The correct option is -1 and -1.

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` `
` `Given the quadratic equation:` `
` `2x2+(k+3)x+2k=0` `
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The correct option is -1 and -1.


We are given the quadratic equation:
2x2+(k+3)x+2k=0


A standard quadratic equation is expressed in the form:
ax2+bx+c=0

By comparing the given equation with the standard quadratic equation, we identify the coefficients as:

a=2

b=k+3

c=2k


Let the roots of the quadratic equation be α and its reciprocal 1α.


The formula for the product of the roots of a quadratic equation is:
Product of roots=ca


Substituting the roots and the values of a and c:
α1α=2k2


1=k

Thus, we find that k=1.


Now, substitute k=1 back into the original quadratic equation:
2x2+(1+3)x+2(1)=0


2x2+4x+2=0


Divide the entire equation by 2:
x2+2x+1=0


Express the left side as a perfect square:
(x+1)2=0


Solving for x:
x=-1,-1

Since the reciprocal of -1 is 1-1=-1, the condition that one root is the reciprocal of the other is satisfied.

Therefore, the roots of the equation are -1 and -1.

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