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Q. The greatest value of $f(x) = \cos \, (xe^{(x)} + 7x^2 - 3x),x \in [-1, \infty )$ is :

Application of Derivatives

Solution:

Given : $f (x) = \cos \, (xe^x + 7x^2 - 3x), x \in [-1, \infty)$
we know that $-1 \le \, \cos \theta \le 1$
$\therefore $ greatest value of cos $\theta$ is 1
Hence, greatest value of $\cos \, (x.e^x + 7x^2 - 3x)$ is 1.