1. **State the problem:** We are given that \((2x + 3)\) is a factor of the cubic polynomial \(4x^3 - 12x^2 - 7x + 30\). We need to find all three solutions to the equation \(4x^3 - 12x^2 - 7x + 30 = 0\).
2. **Use the factor to find one root:** Since \(2x + 3 = 0\) is a factor, solve for \(x\):
$$2x + 3 = 0 \implies x = -\frac{3}{2}$$
This is one root of the cubic equation.
3. **Divide the cubic polynomial by \(2x + 3\) to find the quadratic factor:**
Use polynomial division or synthetic division to divide \(4x^3 - 12x^2 - 7x + 30\) by \(2x + 3\).
Set up the division:
Divide \(4x^3\) by \(2x\) to get \(2x^2\).
Multiply \(2x^2\) by \(2x + 3\):
$$2x^2 \times (2x + 3) = 4x^3 + 6x^2$$
Subtract this from the original polynomial:
$$\cancel{4x^3} - 12x^2 - 7x + 30 - (\cancel{4x^3} + 6x^2) = -18x^2 - 7x + 30$$
Next, divide \(-18x^2\) by \(2x\) to get \(-9x\).
Multiply \(-9x\) by \(2x + 3\):
$$-9x \times (2x + 3) = -18x^2 - 27x$$
Subtract:
$$-18x^2 - 7x + 30 - (-18x^2 - 27x) = 20x + 30$$
Divide \(20x\) by \(2x\) to get \(10\).
Multiply \(10\) by \(2x + 3\):
$$10 \times (2x + 3) = 20x + 30$$
Subtract:
$$20x + 30 - (20x + 30) = 0$$
So the quotient is \(2x^2 - 9x + 10\).
4. **Solve the quadratic equation:**
$$2x^2 - 9x + 10 = 0$$
Use the quadratic formula:
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
where \(a=2\), \(b=-9\), \(c=10\).
Calculate the discriminant:
$$\Delta = (-9)^2 - 4 \times 2 \times 10 = 81 - 80 = 1$$
Calculate the roots:
$$x = \frac{9 \pm \sqrt{1}}{2 \times 2} = \frac{9 \pm 1}{4}$$
So,
$$x_1 = \frac{9 + 1}{4} = \frac{10}{4} = \frac{5}{2}$$
$$x_2 = \frac{9 - 1}{4} = \frac{8}{4} = 2$$
5. **Final solutions:**
The three solutions to \(4x^3 - 12x^2 - 7x + 30 = 0\) are:
$$x = -\frac{3}{2}, \quad x = 2, \quad x = \frac{5}{2}$$
Cubic Roots 77D5A9
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