JEE Main 2022 · 29 Jul · Shift 2 · Mathematics Q12

MathematicsSingle correct+4 / -1Question 12 of 90

The number of elements in the set $S=\left\{x\in\mathbb R:2\cos\left(\dfrac{x^2+x}6\right)=4^x+4^{-x}\right\}$ is :

infinite

Answer and worked solution

Official answer: A

Bounds. The left side is at most 2 and $4^x+4^{-x}\ge2$ , with equality only at $x=0$ , where $2\cos0=2$ . One element.

(A)

Topics:Trigonometric equations AM-GM-HM inequalities

JEE Main 2022 · 29 Jul · Shift 2, Mathematics question 12