Question

Graphically , the pair of equations 7x – y = 5 ; 21x – 3y = 15 represents two lines which are

(a) intersecting at one point (b) parallel lines (c) coincident lines

(d) intersecting at two points​

Answer 1

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Answer 2

These are coincident lines.

Step-by-step explanation:

The pair of equations are

7x - y = 5        (i)  

21x - 3y = 15        (ii)

Before going deeper, let us look at the equations carefully.

The first equation (7x - y = 5)  can be solved for different values of 'x' and 'y' and a corresponding line can be drawn on the graph paper.

Similarly, a line for the second equation can also be drawn.

But, in the given set of equations, we can see that if we take out '3' common from all the terms of equation (ii), we will obtain the equation (i).

Thus, all those values of x and y that satisfy equation (i) will also satisfy equation (ii).

Hence, they will be coincident lines.