Discussion Forum : Application Of Derivatives
Question -


If  a + b +c = 0, then the equation 3ax2+2bx+c=0  has, in the interval (0, 1)

Options:
A .   Atleast one root
B .   Atmost one root
C .   No root
D .   exactly one root
Answer: Option A
:
A
Let f(x)=an Xn+an1 Xn1+...+a2 x2+a1 x+a0
Which is a polynomial function in x of degree n. Hence f(x)  is continuos and differentiable for all x.
Let <β  . We given, f ()=0=f(β).
By Rolle's theorem, f' (c) = 0 for some value c,
<c<β.
Hence the equation
F(x)=nanxn1+(n1)an1xn2+...+a1=0

has atleast one root between  and β.
Hence (c) is the correct answer.

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