The equation of a straight line on a graph is made up of a y term, an x term, and a number and are written in the form of y = mx + c.

The slope of the line is known as the gradient and is represented by m in the equation.

The point at which the line crosses the y-axis is the c in the equation.

When the straight line passes through the origin, c = 0 otherewise the value of c has a number.

So, the straight line y = mx + c is valid for all straight lines.