Q193 / 270 · NDA 2026 (Phase 1) · Mathematics
Consider the following statements :
I. $\sqrt{x}+x+1=0$ has two irrational roots.
II. $5\sqrt{x}-x-4=0$ has two rational roots.
Which of the statements given above is/are correct ?
I. $\sqrt{x}+x+1=0$ has two irrational roots.
II. $5\sqrt{x}-x-4=0$ has two rational roots.
Which of the statements given above is/are correct ?
- AI only
- Correct answerBII only
- CBoth I and II
- DNeither I nor II
Solution
For Statement I:
Let $y = \sqrt{x}$, where $y \ge 0$.
The equation becomes $y^2 + y + 1 = 0$.
The discriminant is $\Delta = 1^2 - 4(1)(1) = -3 < 0$.
Since the discriminant is negative, there are no real roots. Thus, Statement I is incorrect.
For Statement II:
Let $y = \sqrt{x}$, where $y \ge 0$.
The equation becomes $y^2 - 5y + 4 = 0$.
Factoring the quadratic gives $(y - 1)(y - 4) = 0 \Rightarrow y = 1$ or $y = 4$.
Substituting $y = \sqrt{x}$, we get $x = 1$ or $x = 16$.
Both $1$ and $16$ are rational numbers. Thus, Statement II is correct.
Therefore, only Statement II is correct.
Answer: II only
Let $y = \sqrt{x}$, where $y \ge 0$.
The equation becomes $y^2 + y + 1 = 0$.
The discriminant is $\Delta = 1^2 - 4(1)(1) = -3 < 0$.
Since the discriminant is negative, there are no real roots. Thus, Statement I is incorrect.
For Statement II:
Let $y = \sqrt{x}$, where $y \ge 0$.
The equation becomes $y^2 - 5y + 4 = 0$.
Factoring the quadratic gives $(y - 1)(y - 4) = 0 \Rightarrow y = 1$ or $y = 4$.
Substituting $y = \sqrt{x}$, we get $x = 1$ or $x = 16$.
Both $1$ and $16$ are rational numbers. Thus, Statement II is correct.
Therefore, only Statement II is correct.
Answer: II only
Hence, the correct answer is option: 'B'.