Which equation represents a linear function?

equation 1: y = 2x2 + 1
equation 2: y2 = 3x + 1
equation 3: y = 5x3 – 1
equation 4: y = 4x – 1

equation 1
equation 2
equation 3
equation 4

Equations 4.  it is the only one that follows the y=mxplus or minusB formula

All points to the left of zero on a horizontal number line are negative. a number line is a picture of a graduated straight line that serves as abstraction for real numbers. this number line can be extended to the left to represent numbers which are smaller than 0. such numbers are called negative numbersmark me brainliest