Do not use a calculator in answering this question. Solve the inequality
x+4−x2+2x+3<1.\frac{x+4}{-x^2 + 2x + 3} < 1.

  1. (i)

    Deduce the solution of
    x2+4−x4+2x2+3<1,\frac{x^2+4}{-x^4 + 2x^2 + 3} < 1,

  2. (ii)

    x−4x2+2x−3<1.\frac{x-4}{x^2 + 2x - 3} < 1.

Work through it with AI →

It won't just hand you the answer — it asks where you're stuck.How the checker works

Worked solution

4(i)

1. Determine the solution to the main inequality (from the previous part).

From the original inequality x+4−x2+2x+3<1\frac{x+4}{-x^2 + 2x + 3} < 1, we rearrange to get:
x+4−(−x2+2x+3)−x2+2x+3<0\frac{x+4 - (-x^2+2x+3)}{-x^2+2x+3} < 0
x2−x+1−(x−3)(x+1)<0\frac{x^2-x+1}{-(x-3)(x+1)} < 0
Since the discriminant of x2−x+1x^2-x+1 is (−1)2−4(1)(1)=−3<0(-1)^2 - 4(1)(1) = -3 < 0 and the coefficient of x2x^2 is positive, x2−x+1>0x^2-x+1 > 0 for all real xx.
Therefore, −(x−3)(x+1)<0  ⟹  (x−3)(x+1)>0-(x-3)(x+1) < 0 \implies (x-3)(x+1) > 0.
The solution to the main inequality is x<−1 or x>3x < -1 \text{ or } x > 3.

2. Apply the substitution $x \to x^2$ to deduce the new inequality's conditions.

The inequality x2+4−x4+2x2+3<1\frac{x^2+4}{-x^4 + 2x^2 + 3} < 1 is identical to the main inequality with xx replaced by x2x^2.
Substituting x2x^2 into the solution gives:
x2<−1orx2>3x^2 < -1 \quad \text{or} \quad x^2 > 3
Since x2≥0x^2 \ge 0 for all real xx, x2<−1x^2 < -1 has no real solutions.

3. Solve the remaining valid inequality.

We solve x2>3x^2 > 3:
x2−3>0x^2 - 3 > 0
(x−3)(x+3)>0(x - \sqrt{3})(x + \sqrt{3}) > 0
x<−3orx>3x < -\sqrt{3} \quad \text{or} \quad x > \sqrt{3}

Answer

x<−3 or x>3x < -\sqrt{3} \text{ or } x > \sqrt{3}

4(ii)

1. Solve the main inequality from the first part to establish the base solution.

x+4−x2+2x+3−1<0\frac{x+4}{-x^2 + 2x + 3} - 1 < 0
x+4−(−x2+2x+3)−x2+2x+3<0\frac{x+4 - (-x^2 + 2x + 3)}{-x^2 + 2x + 3} < 0
x2−x+1−(x2−2x−3)<0\frac{x^2 - x + 1}{-(x^2 - 2x - 3)} < 0
Since x2−x+1=(x−12)2+34>0x^2 - x + 1 = \left(x - \frac{1}{2}\right)^2 + \frac{3}{4} > 0 for all real xx, the inequality holds when the denominator is negative:
−(x−3)(x+1)<0-(x - 3)(x + 1) < 0
(x−3)(x+1)>0(x - 3)(x + 1) > 0
This gives the base solution: x<−1 or x>3x < -1 \text{ or } x > 3.

2. Relate the target inequality to the original inequality by making a substitution.

Substitute xx with −x-x into the original inequality x+4−x2+2x+3<1\frac{x+4}{-x^2 + 2x + 3} < 1:
(−x)+4−(−x)2+2(−x)+3<1\frac{(-x)+4}{-(-x)^2 + 2(-x) + 3} < 1
−x+4−x2−2x+3<1\frac{-x+4}{-x^2 - 2x + 3} < 1
Multiply the numerator and denominator of the fraction by −1-1:
x−4x2+2x−3<1\frac{x-4}{x^2 + 2x - 3} < 1
This matches the inequality given in part (ii).

3. Deduce the final solution by applying the same substitution to the base solution.

Since the target inequality is formed by replacing xx with −x-x in the original inequality, we replace xx with −x-x in the base solution x<−1 or x>3x < -1 \text{ or } x > 3:
−x<−1or−x>3-x < -1 \quad \text{or} \quad -x > 3
Multiplying by −1-1 and flipping the inequality signs gives:
x>1orx<−3x > 1 \quad \text{or} \quad x < -3

Answer

x<−3 or x>1x < -3 \text{ or } x > 1

AI analysis — may contain mistakes.

Worked this one out on paper? Snap your steps and Gigle's AI math checker will circle the step where it went wrong.

More questions on this topic

  1. 1The sum of the first nn terms of a series is given by Sn=3n(n+2)S_n = 3n(n + 2). Show that this series follows an arithmetic pr…
  2. 2The sum of the first nn terms of a series is given by Sn=3n(n+2)S_n = 3n(n + 2). Show that this series follows an arithmetic pr…
  3. 3Find the exact solution of the inequality 2x+1x2−1≤1.\frac{2x+1}{x^2-1} \le 1. A curve GG has equation ay2+bx3+cx=2ay^2 + bx^3 + cx = 2, w…
  4. 4The curve CC has equation y=x−2kx2+x−2y = \frac{x - 2}{kx^2 + x - 2}, where k>1k > 1. Find the equation of the tangent at the poin…
  5. 5The function gg is defined by g:x↦ln⁡(x−3)g : x \mapsto \ln(x - \sqrt{3}), for x∈Rx \in \mathbb{R}, x>3x > \sqrt{3}. Explain how yo…