Math CentralQuandaries & Queries


Question from Kevin, a student:


Hi Kevin.

You have two equations. One is a horizontal line and the other is a parabola opening downwards:

3x2 + 2y = 11 (parabola)
-36 - y = 11 (horizontal line)

The second equation can easily be solved for y: y = -47.

Now you can substitute what y equals in for the variable y in the first equation. So when you replace y with (-47), you get this:

3x2 + 2(-47) = 11.

Which you can then solve for x and complete the problem (you already know y = -47). Remember that you should get two answers for x.

For more examples of using the substitution method to solve two simultaneous equations, use our Quick Search and look for substitution.

Stephen La Rocque.

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