Question 163280
What are the x-intercept and y-intercept of a linear equation?
An intercept is the point where a line intersects and axis. x intercept is on the x axis; y intercept is on the y axis.
(ii) What are their coordinates on a graph? 
The coordinates are in the form (x,0) for x intercept and (0,y) for y intercept.

Coordinates are the points through which line passes.
(iii) How can they be used to graph a line? 
Any line can be defined and drawn if you know any two points on that line. Assuming a line have both an x and a y intercept, then you have two points. So you can use those two points to draw the line. 

If we are given 2 coordinates of the line, locate the two points. A line joining these two points will be required line.

iv)Demonstrate by determining the intercepts of "14x + 7y = 21".
Set x =0 and solve {{{14*0 + 7y = 21}}}
{{{7y = 21}}}
{{{y = 3}}}
so the y intercept is the point (0,3)

Set y=0 and solve {{{14x + 7*0 = 21}}}
{{{14x = 21}}}
{{{x = 3/2}}}
So the x intercept is the point (3/2, 0)

Now plot those two points and draw the line that includes them
{{{graph(400,400, -5, 5, -5, 5, -2x+3)}}}