How would you solve a simultaneous equation?

Solving a pair of simultaneous equations should ALWAYS begin in labelling each equation. I would go about labelling the first equation (1) and the second (2). A quadratic simulataneous equation question is different to a standard simultaneous equation question with the former being solved by either factorising or utilising the quadratic formula, usually provided by the exam board in the data sheet section at the front/back of the exam paper, and a calculator.

For a standard question, you should first find the lowest common multiple of either the 'x' or 'y' values. You will now have in both equations an 'x' or 'y' that have the same value. Next you need to eliminate the common multiple by either adding or subtracting the two equations. Clearly state what you are doing in this step to the examiner e.g. Eqn. (1) + Eqn. (2). You will be left now with the one value you have not eliminated, simply rearrange the equation to find one of the 'x' or 'y' values. Finally sub in the value you have just worked out into one of the original equations, making it clear to the examiner which value you are substituting into which equation, to find the other 'x' or 'y' value.

DB
Answered by Declan B. Maths tutor

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