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If α and β are the roots of the equation 6x2+x−15=06x^2+x-15=06x2+x−15=0​, where α>β, then the value of (α-β) is:
Question

If α and β are the roots of the equation 6x2+x15=06x^2+x-15=0​, where α>β, then the value of (α-β) is:

A.

203\frac{20}3​​

B.

196\frac{19}6​​

C.

16\frac16​​

D.

13\frac13​​

Correct option is B

Given:  

α\alpha and β\beta are the roots of the equation 6x2+x15=06x^2 + x - 15 = 0 . Where α>β\alpha > \beta​​

Concept Used:

For a quadratic equation of the form ax2+bx+c=0ax^2 + bx + c = 0 the relationships between the sum and product of the roots are given by:

Sum of the roots α+β=ba\alpha + \beta = -\frac{b}{a} 

Product of the roots αβ=ca\alpha \beta = \frac{c}{a} 

Solution:

Let α and β be the roots of this quadratic equation.

For the equation 6x2+x15=06x^2 + x - 15 = 0​  the coefficients are: ​

a = 6 , b = 1 , c = −15 

Thus, we calculate:

α+β=16\alpha + \beta = -\frac{1}{6} 

αβ=156=52\alpha \beta = \frac{-15}{6} = -\frac{5}{2} 

To find α − β, we use the following formula:

(αβ)2=(α+β)24αβ(\alpha - \beta)^2 = (\alpha + \beta)^2 - 4\alpha \beta 

(αβ)2=(16)24(52)(\alpha - \beta)^2 = \left(-\frac{1}{6}\right)^2 - 4\left(-\frac{5}{2}\right) 

(αβ)2=136+10=1+36036=36136(\alpha - \beta)^2 = \frac{1}{36} + 10 = \frac{1+360}{36} = \frac{361}{36} 

αβ=36136=196\alpha - \beta = \sqrt{\frac{361}{36}} = \frac{19}{6} 

Thus the value of αβ\alpha-\beta is 196\frac{19}{6}.​


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