Question

# Find k if one root of the equation $$\displaystyle x^{2}-6kx+8=0$$  is twice the other

A
2
B
±1
C
±12
D
3

Solution

## The correct option is B $$\displaystyle \pm 1$$since the one root is twice the others,Let the one root be a and other root will be 2aNow sum of roots $$a+2a=6k$$and product of roots $$2a^2=8$$$$\therefore a=2,-2$$Now,$$3a=6k$$$$k= \frac{a}{2}$$Now putting the obtained value of a, we get$$k=1,-1$$Maths

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