Mark the correct alternative in the following:

If the polynomial equation a0xn + an–1xn–1 + an–2xn–2 + …. a2x2 + a1x + a0 = 0


n being a positive integer, has two different real roots α and β, then between α and β, the equation n anxn–1 + (n–1) an–1xn–2 + … + a1 = 0 has


As the polynomial, nanxn–1 + (n–1) an–1xn–2 + … + a1 = 0 is a derivative of the polynomial a0xn + an – 1xn – 1 + an – 2xn – 2 +..............a2x2 + a1x + a0 = 0 --------- (i)


Putting x = 0 in equation (i),


f(0) = a0 < 0, {Y – Intercept of the graph is negative}


On the other hand, an > 0 and ‘n’ is even, the leading term on xn, is positive for only x.


For |x| to be large, the term anxn will dominate, so


lim x-∞ f (x) = +∞


lim x+∞ f (x) = +∞


If lim x+∞ f (x) = +∞, there must exist


Same number α < 0, where f(α > 0)


f(0) = a0 < 0,


α < β < 0, such that f(β) = 0


Also, there is some value 0 < α,


Where f(a) & so there exists,


0 < b < a with f(b) = 0


Additionally, the polynomial function (equation (i)) is continuous everywhere in R and consequently derivative in R.


a0xn + an – 1xn – 1 + an – 2xn – 2 +..............a2x2 + a1x + a0 = 0 is continuous on α,β and derivative on α,β.


Thus, it satisfies both the conditions of Rolle' s Theorem.


As per the Rolle’s Theorem, between any two roots of a function f(x), there exists at least one root of its derivative.


Thus, the equation nanxn–1 + (n–1) an–1xn–2 + … + a1 = 0 will have at least one root between α & β.


Hence, Option (C) is the answer.

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