Quadratic Equations
1. **Problem 1.1: Solve the quadratic equation** $$x^2 + 14x + 45 = 0$$
Step 1: Identify coefficients: $$a=1$$, $$b=14$$, and $$c=45$$.
Step 2: Calculate the discriminant $$\Delta$$ using $$\Delta = b^2 - 4ac$$:
$$\Delta = 14^2 - 4\times1\times45 = 196 - 180 = 16$$.
Step 3: Since $$\Delta > 0$$, the equation has two real roots.
Step 4: Use quadratic formula $$x = \frac{-b \pm \sqrt{\Delta}}{2a}$$:
$$x = \frac{-14 \pm \sqrt{16}}{2} = \frac{-14 \pm 4}{2}$$.
Step 5: Calculate roots:
- $$x_1 = \frac{-14 + 4}{2} = \frac{-10}{2} = -5$$
- $$x_2 = \frac{-14 - 4}{2} = \frac{-18}{2} = -9$$
**Answer:** $$x = -5$$ or $$x = -9$$.
2. **Problem 1.2: Factorize the expressions**
a) $$x^2 + 12x + 36$$
Step 1: Recognize this as a perfect square trinomial: $$(x + 6)^2$$ because $$6 \times 6 = 36$$ and $$6 + 6 = 12$$.
**Answer:** $$(x + 6)^2$$
b) $$x^2 - 25$$
Step 1: Recognize it as a difference of squares:
$$x^2 - 25 = (x)^2 - (5)^2$$
Step 2: Apply difference of squares factorization:
$$(x - 5)(x + 5)$$
**Answer:** $$(x - 5)(x + 5)$$
3. **Problem 1.3: Rectangle dimensions given area and length-width relation**
Step 1: Let width be $$w$$ cm, then length is $$w + 2$$ cm.
Step 2: Area $$A = \text{length} \times \text{width} = (w + 2)w = 8$$
Step 3: Form quadratic equation:
$$w^2 + 2w = 8$$
Rewrite as:
$$w^2 + 2w - 8 = 0$$
Step 4: Factorize or use quadratic formula:
Calculate discriminant:
$$\Delta = 2^2 - 4\times1\times(-8) = 4 + 32 = 36$$
Step 5: Use quadratic formula:
$$w = \frac{-2 \pm \sqrt{36}}{2} = \frac{-2 \pm 6}{2}$$
Step 6: Calculate roots:
- $$w_1 = \frac{-2 + 6}{2} = \frac{4}{2} = 2$$
- $$w_2 = \frac{-2 - 6}{2} = \frac{-8}{2} = -4$$ (discard negative width)
Step 7: Length is $$w + 2 = 2 + 2 = 4$$ cm.
**Answer:** Width = 2 cm, Length = 4 cm.