Relative Error
1. **State the problem:** We want to find the relative error when approximating the expression $5x^2 - 1$ using 4-digit chopping for $x = 11110.3338$.
2. **Recall the formula for relative error:**
$$\text{Relative error} = \frac{|\text{Exact value} - \text{Approximate value}|}{|\text{Exact value}|}$$
3. **Calculate the exact value:**
$$x = 11110.3338$$
$$5x^2 - 1 = 5 \times (11110.3338)^2 - 1$$
First, calculate $x^2$:
$$11110.3338^2 = 123456790.1115 \text{ (approx)}$$
Then multiply by 5 and subtract 1:
$$5 \times 123456790.1115 - 1 = 617283945.5575$$
4. **Calculate the approximate value using 4-digit chopping:**
Chop $x$ to 4 digits:
$$x_{chopped} = 11110$$
Calculate $x_{chopped}^2$:
$$11110^2 = 123432100$$
Calculate approximate value:
$$5 \times 123432100 - 1 = 617160499$$
5. **Calculate the relative error:**
$$\text{Relative error} = \frac{|617283945.5575 - 617160499|}{|617283945.5575|} = \frac{123446.5575}{617283945.5575} \approx 0.0002$$
6. **Interpretation:** The relative error is approximately $0.0002$, which means the 4-digit chopping approximation introduces a small error of about 0.02%.