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प्रश्न
If one root the equation 2x2 + kx + 4 = 0 is 2, then the other root is
विकल्प
6
-6
-1
1
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उत्तर
Let `alpha and beta `be the roots of quadratic equation`2x^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)/2`in above
`2 xx (-k - 4)/ 2 = 2`
`(-k - 4) = 2`
` k = -4 -2`
`= -6`
Putting the value of k in `beta = (-k - 4)/2`
`beta = (-(6) - 4)/2`
`= (6-4)/2`
` = 2/2`
`beta = 1`
Therefore, value of other root be `beta = 1`
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