The equation y = 3x + 4 represents a linear function, because it is in the standard form of a linear equation, y = mx + b, where m is the slope and b is the y-intercept. In this case, the slope is 3, which means that for every unit increase in x, there is a corresponding increase of 3 units in y. The y-intercept is 4, which is the value of y when x equals 0.
The graph of a linear function is a straight line, and the equation y = 3x + 4 represents a straight line with a slope of 3 and a y-intercept of 4. Therefore, the function is linear.