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  • If the sum of the roots of a quadratic equation is 2 and the sum of their cubes is 98, then the equation is ?

If the sum of the roots of a quadratic equation is 2 and the sum of their cubes is 98, then the equation is ?

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best_answer

So let the roots be 
a,b

so given 
a + b = 2
and

Sum of their cubes = 98 : a³+b³=98

(a+b)³ = a³ + b³ + 3ab × (a+b)
⇒2³ = 98 + 3ab(2)
⇒ 8 = 98 + 6 ab
⇒ 6ab = 8-98 =-90
⇒ ab = -90/6 
⇒ ab = -15


So equation is x² - 2x -15 = 0
 

Posted by

himanshu.meshram

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