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Inequality LEVEL- 1
Q1–10 of 50
1

Solve the following inequality :

3x² – 7x + 4 ≤ 0

Correct Answer: D. None of these
Explanation:


  • Step 1: Factor the quadratic expression:

    $$3x^2 - 3x - 4x + 4 \le 0 \implies 3x(x - 1) - 4(x - 1) \le 0 \implies (3x - 4)(x - 1) \le 0$$
  • Step 2: The roots are $x = 1$ and $x = \frac{4}{3}$. Since it is $\le 0$, the solution lies between the roots:

    $$1 \le x \le \frac{4}{3}$$
  • 2

    Solve the following inequality:

    3x² – 7x – 6 < 0

    Correct Answer: A. –0.66 < x < 3
    Explanation:


  • Step 1: Factor the quadratic expression:

    $$3x^2 - 9x + 2x - 6 < 0 \implies 3x(x - 3) + 2(x - 3) < 0 \implies (3x + 2)(x - 3) < 0$$
  • Step 2: The critical values are $x = -\frac{2}{3} \approx -0.666...$ and $x = 3$.

  • Step 3: For the inequality to be negative, $x$ must lie between the roots:

    $$-\frac{2}{3} < x < 3 \quad \implies \quad -0.66 < x < 3$$
  • 3

    Solve the following inequality :
    3x² – 7x + 6 < 0

    Correct Answer: D. None of these
    Explanation:


  • Step 1: Calculate the discriminant $D = b^2 - 4ac$:

    $$D = (-7)^2 - 4(3)(6) = 49 - 72 = -23$$
  • Step 2: Since $D < 0$ and the leading coefficient $a = 3 > 0$, the quadratic expression is positive for all real $x$. Therefore, $3x^2 - 7x + 6$ can never be less than zero.

  • 4

    Solve the following inequality :
    x² – 3x + 5 > 0

    Correct Answer: D. –∞ < x < ∞
    Explanation:


  • Step 1: Calculate the discriminant:

    $$D = (-3)^2 - 4(1)(5) = 9 - 20 = -11$$
  • Step 2: Since $D < 0$ and $a = 1 > 0$, the parabola opens upwards and never crosses the x-axis. Thus, the expression is always positive for all real $x$.

  • 5

    Solve the following inequality :
    x² – 14x – 15 > 0

    Correct Answer: C. Both (a) and (b)
    Explanation:


  • Step 1: Factor the expression:

    $$(x - 15)(x + 1) > 0$$
  • Step 2: The roots are $x = -1$ and $x = 15$. For the product to be positive, $x$ must lie outside the roots:

    $$x < -1 \quad \text{or} \quad x > 15$$
  • 6

    Solve the following inequality :
    2 – x – x² ≥ 0

    Correct Answer: A. –2 ≤ x ≤ 1
    Explanation:


  • Step 1: Multiply the inequality by $-1$ (and flip the inequality sign):

    $$x^2 + x - 2 \le 0$$
  • Step 2: Factor:

    $$(x + 2)(x - 1) \le 0$$
  • Step 3: The roots are $x = -2$ and $x = 1$. The solution is:

    $$-2 \le x \le 1$$
  • 7

    Solve the following inequality :
    |x² – 4x| < 5

    Correct Answer: D. –1 < x < 5
    Explanation:


  • Step 1: Split into double inequalities: $-5 < x^2 - 4x < 5$.

  • Part A: $x^2 - 4x > -5 \implies x^2 - 4x + 5 > 0$.

    • Discriminant $D = 16 - 20 = -4 < 0$. Holds true for all real $x$.

  • Part B: $x^2 - 4x < 5 \implies x^2 - 4x - 5 < 0 \implies (x - 5)(x + 1) < 0$.

    • Solution: $-1 < x < 5$.

  • Answer: (d) –1 < x < 5

  • 8

    Solve the following inequality :
    |x² + x| – 5 < 0

    Correct Answer: D. None of these
    Explanation:


  • Step 1: Rearrange to $\vert{}x^2 + x\vert{} < 5 \implies -5 < x^2 + x < 5$.

  • Part A: $x^2 + x + 5 > 0$ ($D = 1 - 20 < 0$, true for all real $x$).

  • Part B: $x^2 + x - 5 < 0$.

    • Roots are $x = \frac{-1 \pm \sqrt{21}}{2}$.

    • Solution is $\frac{-1 - \sqrt{21}}{2} < x < \frac{-1 + \sqrt{21}}{2}$.

  • Conclusion: None of the listed options reflect this boundary range.

  • 9

    Solve the following inequality :
    |x² – 5x| < 6

    Correct Answer: C. Both (a) and (b)
    Explanation:


  • Step 1: Double inequality: $-6 < x^2 - 5x < 6$.

  • Part A: $x^2 - 5x + 6 > 0 \implies (x - 2)(x - 3) > 0 \implies x < 2 \text{ or } x > 3$.

  • Part B: $x^2 - 5x - 6 < 0 \implies (x - 6)(x + 1) < 0 \implies -1 < x < 6$.

  • Intersection of Part A and B: $(-1 < x < 2) \cup (3 < x < 6)$

  • 10

    Solve the following inequality :
    |x² – 2x| < x

    Correct Answer: A. 1 < x < 3
    Explanation:


  • Step 1: Since absolute value is non-negative, $x > 0$.

  • Step 2: $-x < x^2 - 2x < x$.

    • Left: $x^2 - x > 0 \implies x(x - 1) > 0$. Since $x > 0$, this requires $x > 1$.

    • Right: $x^2 - 3x < 0 \implies x(x - 3) < 0$. Since $x > 0$, this requires $x < 3$.

  • Step 3: Combining yields $1 < x < 3$.

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