Question: The equations of four lines are given. Identify which lines are parallel.
Line 1: $y = -5x - 5$
Line 2: $x + \frac{1}{2} y = -4$
Line 3: $y = -2x + 4$
Line 4: $y + 8 = -\frac{1}{5} (x - 9)$
1. **State the problem:** We need to find which lines among the four given are parallel.
2. **Recall the rule:** Lines are parallel if and only if their slopes are equal.
3. **Find the slope of each line:**
- Line 1 is already in slope-intercept form $y = mx + b$ with slope $m = -5$.
- Line 2: Given $x + \frac{1}{2} y = -4$.
Solve for $y$:
$$\frac{1}{2} y = -4 - x$$
$$y = 2(-4 - x) = -2x - 8$$
So slope $m = -2$.
- Line 3 is given as $y = -2x + 4$, slope $m = -2$.
- Line 4: Given $y + 8 = -\frac{1}{5} (x - 9)$.
Expand right side:
$$y + 8 = -\frac{1}{5} x + \frac{9}{5}$$
Subtract 8:
$$y = -\frac{1}{5} x + \frac{9}{5} - 8 = -\frac{1}{5} x - \frac{31}{5}$$
So slope $m = -\frac{1}{5}$.
4. **Compare slopes:**
- Line 1 slope: $-5$
- Line 2 slope: $-2$
- Line 3 slope: $-2$
- Line 4 slope: $-\frac{1}{5}$
Lines 2 and 3 have the same slope $-2$, so they are parallel.
5. **Final answer:** Lines 2 and 3 are parallel.