constant - 

a term that does not vary

coefficient - 

the multiplier of a specified variable in a term

gradient - 

a measure of how steep a line is

intercept - 

the point where a line crosses a specified axis

origin - 

the point with coordinates (0, 0)

equation of a straight line - 

a relationship which, when plotted, forms a straight line

$$y = 3x − 2$$ - 

gradient 3, $$y$$-intercept (0, -2)

$$y = 3x + 2$$ - 

gradient 3, $$y$$-intercept (0, 2)

$$y = 2 - 3x$$ - 

gradient -3, $$y$$-intercept (0, 2)

$$y = 2x - 3$$ - 

gradient 2, $$y$$-intercept (0, -3)

$$y = 3 + 2x$$ - 

gradient 2, $$y$$-intercept (0, 3)

$$y = 3 - 2x$$ - 

gradient -2, $$y$$-intercept (0, 3)

A (blue) - 

$$y=-{2\over 3}x - 2$$

B (pink) - 

$$y=-{3\over 2}x - 2$$

C (black) - 

$$y={3\over 2}x $$

D (green) - 

$$y={3\over 2}x - 2$$

E (purple) - 

$$y={2\over 3}x - 2$$