Math CentralQuandaries & Queries


Question from Stephanie, a student:

Find the point of intersection of the pair of straight lines:
x = _______ and y = ________

I am totally confused. Please help


The intersection is the place where both equations are true. If you add or subtract the equations (or multiply both sides by the same constant) you get more true equations, some of which will be simpler.

So at the point of intersection you also have (among many other choices)

2y = -6x -18 (multiply the first by 2)
y = -4x -2 (multiply second by -1)
-7y = 28x + 14 (multiply second by 7)
0 = x-7 (add them)
2y = -7x -11 (subtract second from first)

Do any of these look easier? Over to you.

Good Hunting!


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