If \( y = 4x + 3 \) is changed to \( y = -4x + 3 \), the graph of the new function would be a reflection of the original graph across the y-axis. This change in the sign of the coefficient of x (from positive to negative) affects the slope of the line, resulting in a line that slopes downward instead of upward.
In summary, the new function will have the same y-intercept (3) but will slope downwards instead of upwards.