CAT 2003 Slot 1 — QA Question 22
Each question is followed by two statements, A and B. Answer each question using the following instructions
Choose 1 if the question can be answered by using one of the statements alone but not by using the other statement alone.
Choose 2 if the question can be answered by using either of the statements alone.
Choose 3 if the question can be answered by using both statements together but not by either statement alone.
Choose 4 if the question cannot be answered on the basis of the two statements.
What are the unique values of b and c in the equation 4x2 + bx + c = 0 if one of the roots of the equation is (−1/2)?
A. The second root is 1/2
B. The ratio of c and b is 1
Answer & solution
- A
1
2
- C
3
- D
4
4x2 + bx + c = 0 …(i)
One root = −1/2
Using statement A alone:
Second root is 1/2.
Sum of the roots = −b/4 = (−1/2) + 1/2 = 0
∴ b = 0
Also, product of the roots = c/4 = (−1/2) × (1/2) = (−1/4)
∴ c = −1
So, statement A alone is sufficient to answer the question.
Using statement B alone:
Ratio of c and b is 1.
∴ b = c
∴ Equation (i) becomes 4x2 + bx + b = 0 ...(ii)
But one root = −1/2
Substituting x = −1/2 in the above equation (ii), we get,
1 − b/2 + b = 0
∴ b = −2 and c = −2
So, statement B alone is also sufficient to answer the question.
Hence, option (b).