GCSE Style Question and Answer 3

Solve the following pair of simultaneous equations.

4x+3y=7 and 3x+4y=7

Multiply the top equation by 3 throughout, and the bottom equation by 4 throughout.

We now have 12x in both equations, so we can subtract them to eliminate x.

Only the y terms remain on the LHS, and as you can see, it is a simple matter of solving for y.

Substituting y into 4x+3y=7 allows us to solve for x. Not surprisingly, x=1, and y=1. You could have figured that out without going through the calculations, however beginners will not notice the obvious solutions.