Find the equations of straight lines which pass through `(2,1)` and are respectively parallel and perpendicular to the x-axis.

Answer

To find the equations of straight lines that pass through the point (2, 1) and are respectively parallel and perpendicular to the x-axis, we will consider two cases.

### Step 1: Equation of the line parallel to the x-axis
A line that is parallel to the x-axis has a constant y-value. Since the line must pass through the point (2, 1), the y-coordinate of this point will be the y-value of the line.

**Solution:**
- The equation of the line parallel to the x-axis that passes through (2, 1) is:
\[ y = 1 \]

### Step 2: Equation of the line perpendicular to the x-axis
A line that is perpendicular to the x-axis is vertical and has a constant x-value. Since the line must pass through the point (2, 1), the x-coordinate of this point will be the x-value of the line.

**Solution:**
- The equation of the line perpendicular to the x-axis that passes through (2, 1) is:
\[ x = 2 \]

### Final Answer:
- The equation of the line parallel to the x-axis is \( y = 1 \).
- The equation of the line perpendicular to the x-axis is \( x = 2 \).