1
BITSAT 2025
MCQ (Single Correct Answer)
+3
-1

If ' $a$ ' is a complex number such that $|a|=1$. Find the value of $a$, so that the equation $a z^2+z+1=0$ has one purely imaginary root.

A

$\cos \left\{\cos ^{-1}\left(\frac{-\sqrt{5}+1}{4}\right)\right\}$

B

$\cos \left\{\sin ^{-1}\left(\frac{\sqrt{5}+1}{4}\right)\right\}+i \sin \left\{\cos ^{-1}\left(\frac{\sqrt{5}+1}{4}\right)\right\}$

C

$\sin \left\{\cos ^{-1}\left(\frac{\sqrt{5}-1}{4}\right)\right\}+i \sin ^{-1}\left(\frac{-\sqrt{5}+1}{2}\right)$

D

None of the above

2
BITSAT 2025
MCQ (Single Correct Answer)
+3
-1

If $\mathbf{a , b , c}$ are vectors such that $|\mathbf{b}|=|\mathbf{c}|$ then $\{(\mathbf{a}+\mathbf{b}) \times(\mathbf{a}+\mathbf{c})\} \times(\mathbf{b} \times \mathbf{c}) \cdot(\mathbf{b}+\mathbf{c})$ is equal to

A

1

B

4

C

2

D

0

3
BITSAT 2025
MCQ (Single Correct Answer)
+3
-1

For what value of $a, 6$ lies between the roots of the equation $x^2+2(a-3) x+9=0$.

A

$\left(\frac{-3}{4}, \infty\right)$

B

$\left(-\infty, \frac{-3}{4}\right) \cup(2, \infty)$

C

$\left(-\infty, \frac{-3}{4}\right)$

D

$\left(\frac{3}{4}, \infty\right)$

4
BITSAT 2025
MCQ (Single Correct Answer)
+3
-1

What is the probability of getting a sum of 9 in a single throw of three fair dice?

A

$\frac{6}{216}$

B

$\frac{36}{216}$

C

$\frac{9}{216}$

D

$\frac{25}{216}$

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