Sign change - Polynomial Inequality

Rarely Tested

  • Wavy curve method for solving (xβˆ’a)(xβˆ’b)(xβˆ’c) > 0
  • Arrange the critical points in ascending order.
    $$a<b<c$$
  • Number line representation:


  • $$(x-a)(x-b)(x-c) > 0 \Rightarrow x \in (a,b)\cup(c,\infty)$$

Question 1

$$f(x) = \frac{x^2 + 2x - 15}{x^2 - 7x - 18}$$ is negative if and only if

Question 2

The number of integer solutions of the equation $$\left(x^{2} - 10\right)^{\left(x^{2}- 3x- 10\right)} = 1$$ is

Question 3

Any non-zero real numbers x,y such that $$y\neq3$$ and $$\frac{x}{y}<\frac{x+3}{y-3}$$, Will satisfy the condition.

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