Simplify the equation if possible. State whether the equation represents a horizontal or a vertical line. Then graph the equation. \[ 7 y+21=0 \]

To simplify the equation \( 7y + 21 = 0 \), we can first isolate \( y \). Subtract 21 from both sides: \[ 7y = -21 \] Next, divide both sides by 7: \[ y = -3 \] This equation represents a horizontal line at \( y = -3 \) because \( y \) has a constant value regardless of \( x \). When you graph this equation, you draw a straight horizontal line across the Cartesian plane at \( y = -3 \), passing through all points with that \( y \)-value. Imagine it like a bright, sunny day at the beach, with a long, picturesque horizon stretching on! It stays consistent and unchanging, just like your horizontal line!