Answer :

To solve the inequality [tex]\(4x^3 + 20x^2 - 9x - 45 > 0\)[/tex], we can approach it by analyzing the polynomial function and using intervals where the function is positive. Here's how:

1. Identify the Signs of the Polynomial:
- We need to find the intervals where the polynomial [tex]\(4x^3 + 20x^2 - 9x - 45\)[/tex] is greater than zero.

2. Find the Critical Points (Roots):
- To do this, we first find the roots of the equation [tex]\(4x^3 + 20x^2 - 9x - 45 = 0\)[/tex]. These roots divide the number line into intervals that we can test.
- Assume we find the roots to be [tex]\(a\)[/tex], [tex]\(b\)[/tex], and potentially [tex]\(c\)[/tex].

3. Test the Intervals:
- The roots divide the number line into intervals. Typically, we check the sign of the polynomial in each interval.
- The intervals we are interested in come from considering the sorted roots and checking between and beyond them.

4. Determine Where the Polynomial is Positive:
- Analyze the intervals: if we assume the roots found are [tex]\(-5\)[/tex], [tex]\(-\frac{3}{2}\)[/tex], and [tex]\(\frac{3}{2}\)[/tex], then the intervals are:
- [tex]\((-5, -\frac{3}{2})\)[/tex]
- [tex]\((-\frac{3}{2}, \frac{3}{2})\)[/tex]
- [tex]\((\frac{3}{2}, \infty)\)[/tex]
- Evaluate the sign of the polynomial in each interval.

5. Construct the Solution:
- Through your interval analysis, you'll find that the polynomial [tex]\(4x^3 + 20x^2 - 9x - 45\)[/tex] is positive in:
- The interval [tex]\((-5, -\frac{3}{2})\)[/tex]
- The interval [tex]\((\frac{3}{2}, \infty)\)[/tex]

Therefore, the solution to the inequality [tex]\(4x^3 + 20x^2 - 9x - 45 > 0\)[/tex] is:
- For [tex]\(x\)[/tex] in the interval [tex]\((-5, -\frac{3}{2})\)[/tex].
- For [tex]\(x\)[/tex] in the interval [tex]\((\frac{3}{2}, \infty)\)[/tex].

This means the polynomial is positive in these regions of [tex]\(x\)[/tex], and any [tex]\(x\)[/tex] values within these intervals will satisfy the given inequality.

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Rewritten by : Barada