Question
Let $$P\left( x \right) = {a_0} + {a_1}{x^2} + {a_2}{x^4} + ..... + {a_n}{x^{2n}}$$ be a polynomial in a real variable $$x$$ with $$0 < {a_0} < {a_1} < {a_2} < ..... < {a_n}.$$ The function $$P\left( x \right)$$ has :
A.
neither a maximum nor a minimum
B.
only one maximum
C.
only one minimum
D.
only one maximum and only one minimum
Answer :
only one minimum
Solution :
The given polynomial is
$$P\left( x \right) = {a_0} + {a_1}{x^2} + {a_2}{x^4} + ..... + {a_n}{x^{2n}},\,x\, \in \,R{\text{ and }}\,0 < {a_0} < {a_1} < {a_2} < ..... < {a_n}.$$
Here, we observe that all coefficients of different powers of $$x,$$ i.e., $${a_0},\,{a_1},\,{a_2},\,.....,{a_n},$$ are positive.
Also, only even powers of $$x$$ are involved.
Therefore, $$P\left( x \right)$$ cannot have any maximum value.
Moreover, $$P\left( x \right)$$ is minimum, when $$x = 0,$$ i.e., $${a_0}.$$
.
Therefore, $$P\left( x \right)$$ has only one minimum.