The Math Handbook by Richard Elwes

Author:Richard Elwes [Elwes, Richard]
Language: eng
Format: epub
Publisher: Quercus
Published: 2013-09-27T16:00:00+00:00

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IF YOU THINK YOU CAN MANAGE THAT, TRY QUIZ 2.

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All that remains is to divide both sides by 4. Dividing 4x by 4 leaves x alone on the left-hand side, which is exactly what we were aiming for. Dividing 20 by 4 gives 5. So we end up with:

x = 5

One of the good things about equations is that you do not need anyone to tell you whether you have got it right. It is easy to check, and I would suggest that you always do this. If our solution above is correct, then if we take the original equation 4x − 3 = 17, and substitute in the value X = 5, we should get a true statement. If we don’t, then we know we have made a mistake. So let’s try: 4 × 5 − 3 = 17; this is true, so we have solved the equation correctly.

If we were presented directly with the equation 4x − 3 = 17, how would we know where to start: which move needs to be undone first? The two options are multiplication by 4 and subtraction by 3. An old friend comes to our assistance: BEDMAS (see The language of mathematics). That tells us that the multiplication was done first, followed by the subtraction. So, to undo these steps, we go in reverse order and tackle the −3 first.

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