Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Relations and Functions

Question:

The domain of the real valued function f(x) for which $4^{f(x)}+4^{1-f(x)}=4^x$ is

Options:

(-1 , 1]

[1, ∞)

(-∞, 1]

(-∞, -1]

Correct Answer:

[1, ∞)

Explanation:

$4^{f(x)}+\frac{4}{4^{f(x)}}=4^x$

$(4^{f(x)})^2-4^{xf(x)}+4=0⇒u^2-4^xu+4=0\,\,\,∵D≥0$

$4^{2x}≥4^2⇒2x≥2⇒x≥1$