Question: y = e^2x and y = 5 - 4x
1
5/4
The two graphs intersect once, e^x = 5/4 has 1 real root.
2(b) Show by Calculation that the root of the eqn is (as lies between 0 and 1.
(c) Use the NRM method, starting with x₀ = 0,5 to find the root of e^2x + 4x - 5 = 0 to 2 d-places.
1. **State the problem:** Find the root of the equation $$e^{2x} + 4x - 5 = 0$$ which corresponds to the intersection of the curves $$y = e^{2x}$$ and $$y = 5 - 4x$$.
2. **Show the root lies between 0 and 1:**
Evaluate the function $$f(x) = e^{2x} + 4x - 5$$ at $$x=0$$ and $$x=1$$:
$$f(0) = e^{0} + 0 - 5 = 1 - 5 = -4$$
$$f(1) = e^{2} + 4 - 5 = e^{2} - 1 \approx 7.389 - 1 = 6.389$$
Since $$f(0) < 0$$ and $$f(1) > 0$$, by the Intermediate Value Theorem, there is at least one root between $$0$$ and $$1$$.
3. **Newton-Raphson Method (NRM):**
The formula for NRM is:
$$x_{n+1} = x_n - \frac{f(x_n)}{f'(x_n)}$$
Here,
$$f(x) = e^{2x} + 4x - 5$$
$$f'(x) = 2e^{2x} + 4$$
4. **Start with $$x_0 = 0.5$$:**
- Calculate $$f(0.5)$$:
$$f(0.5) = e^{1} + 2 - 5 = e^{1} - 3 \approx 2.718 - 3 = -0.282$$
- Calculate $$f'(0.5)$$:
$$f'(0.5) = 2e^{1} + 4 = 2 \times 2.718 + 4 = 5.436 + 4 = 9.436$$
- Apply NRM formula:
$$x_1 = 0.5 - \frac{-0.282}{9.436} = 0.5 + 0.0299 = 0.5299$$
5. **Second iteration:**
- Calculate $$f(0.5299)$$:
$$f(0.5299) = e^{2 \times 0.5299} + 4 \times 0.5299 - 5 = e^{1.0598} + 2.1196 - 5$$
$$\approx 2.886 + 2.1196 - 5 = 0.0056$$
- Calculate $$f'(0.5299)$$:
$$f'(0.5299) = 2e^{1.0598} + 4 = 2 \times 2.886 + 4 = 5.772 + 4 = 9.772$$
- Apply NRM formula:
$$x_2 = 0.5299 - \frac{0.0056}{9.772} = 0.5299 - 0.00057 = 0.5293$$
6. **Third iteration:**
- Calculate $$f(0.5293)$$:
$$f(0.5293) = e^{1.0586} + 4 \times 0.5293 - 5 \approx 2.883 + 2.117 - 5 = 0.0000$$
- Since $$f(0.5293) \approx 0$$, the root is approximately $$x = 0.53$$ to 2 decimal places.
**Final answer:** The root of $$e^{2x} + 4x - 5 = 0$$ is approximately $$x = 0.53$$.