1
JEE Main 2022 (Online) 25th June Morning Shift
+4
-1

Let f : N $$\to$$ R be a function such that $$f(x + y) = 2f(x)f(y)$$ for natural numbers x and y. If f(1) = 2, then the value of $$\alpha$$ for which

$$\sum\limits_{k = 1}^{10} {f(\alpha + k) = {{512} \over 3}({2^{20}} - 1)}$$

holds, is :

A
2
B
3
C
4
D
6
2
JEE Main 2022 (Online) 25th June Morning Shift
+4
-1

Let $$f:R \to R$$ and $$g:R \to R$$ be two functions defined by $$f(x) = {\log _e}({x^2} + 1) - {e^{ - x}} + 1$$ and $$g(x) = {{1 - 2{e^{2x}}} \over {{e^x}}}$$. Then, for which of the following range of $$\alpha$$, the inequality $$f\left( {g\left( {{{{{(\alpha - 1)}^2}} \over 3}} \right)} \right) > f\left( {g\left( {\alpha -{5 \over 3}} \right)} \right)$$ holds ?

A
(2, 3)
B
($$-$$2, $$-$$1)
C
(1, 2)
D
($$-$$1, 1)
3
JEE Main 2021 (Online) 1st September Evening Shift
+4
-1
The range of the function,

$$f(x) = {\log _{\sqrt 5 }}\left( {3 + \cos \left( {{{3\pi } \over 4} + x} \right) + \cos \left( {{\pi \over 4} + x} \right) + \cos \left( {{\pi \over 4} - x} \right) - \cos \left( {{{3\pi } \over 4} - x} \right)} \right)$$ is :
A
$$\left( {0,\sqrt 5 } \right)$$
B
[$$-$$2, 2]
C
$$\left[ {{1 \over {\sqrt 5 }},\sqrt 5 } \right]$$
D
[0, 2]
4
JEE Main 2021 (Online) 31st August Evening Shift
+4
-1
Let f : N $$\to$$ N be a function such that f(m + n) = f(m) + f(n) for every m, n$$\in$$N. If f(6) = 18, then f(2) . f(3) is equal to :
A
6
B
54
C
18
D
36
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