There are two standard forms and the format you presented is that of: #y=mx+c#

#y# is the dependant variable. Its value is 'dependant' on what value you assign to #x#

#x# is the independent variable to which you may assign any value you so chose, unless restricted by the conditions of the question.

#m# is the gradient (slope) which is always read from left to right on the x-axis. It is : #("change in up or down")/("change in along")#

#c# is the constant and in this equation type and it is where the plotted line crosses the y-axis.

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The other standard form uses just #m# in relation to 2 fixed points. The value of #c# is directly related to these points, thus can be determined by algebraic manipulation.

Let point 1 be #P_1->(x_1,y_1)#

Let point 2 be #P_2->(x_2,y_2)#

Then the equation takes the form:

#m=(y_2-y_1)/(x_2-x_1)#