Maths · Algebra and graphs. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
To solve an equation is to find the value of the letter that makes it true. Keep the equation balanced: whatever you do to one side, do to the other. If there are fractions, multiply every term by the common denominator first to remove them.
Simultaneous equations have two unknowns. Make the number in front of one letter the same in both equations, then add or subtract to remove that letter. Or use substitution.
A quadratic equation must equal zero before you solve it. Then factorise, complete the square or use the formula. It usually has two solutions. To change the subject of a formula, use the same balancing steps to get the wanted letter alone.
In the quadratic formula, students get the signs wrong when b or c is negative, or divide only the root by 2a. Put negative values in brackets, and divide the whole of −b ± √(b2 − 4ac) by 2a.
Answer: x = 0.18 or x = −1.85
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