1
WB JEE 2019
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Let $$f:R \to R$$ be defined by $$f(x) = {x^2} - {{{x^2}} \over {1 + {x^2}}}$$ for all $$x \in R$$. Then,
A
f is one-one but not onto mapping
B
f is onto but not one-one mapping
C
f is both one-one and onto
D
f is neither one-one nor onto
2
WB JEE 2019
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Let the relation $$\rho $$ be defined on R as a$$\rho $$b if 1 + ab > 0. Then,
A
$$\rho $$ is reflexive only.
B
$$\rho $$ is equivalence relation.
C
$$\rho $$ is reflective and transitive but not symmetric.
D
$$\rho $$ is reflexive and symmetric but not transitive.
3
WB JEE 2019
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A problem in mathematics is given to 4 students whose chances of solving individually are $${{1 \over 2}}$$, $${{1 \over 3}}$$, $${{1 \over 4}}$$ and $${{1 \over 5}}$$. The probability that the problem will be solved at least by one student is
A
$${{2 \over 3}}$$
B
$${{3 \over 5}}$$
C
$${{4 \over 5}}$$
D
$${{3 \over 4}}$$
4
WB JEE 2019
MCQ (Single Correct Answer)
+1
-0.25
Change Language
If X is a random variable such that $$\sigma$$(X) = 2.6, then $$\sigma$$(1 $$-$$ 4X) is equal to
A
7.8
B
$$-$$ 10.4
C
13
D
10.4
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