Multiplying Binomials Using FOIL
The hardest thing about multiplying binomials is keeping track of all the numbers. It can be easy to forget one step in the multiplication process, or even to multiply something twice. The FOIL method gives you a way to keep track of the steps in multiplying binomials. It is an easy acronym to remember, which makes it the perfect tool to cut down on math mistakes.
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Instructions
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Learn what FOIL means. Foil is an acronym standing for "first, outer, inner, last." It is the order in which you learn to multiply the numbers in two binomials. Having a set order in which to do your multiplication will help you keep track of the numbers and not forget anything.
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Multiply the first two numbers. For example, if you have the mathematical expression (x + 2)(x - 3), you multiply the first term from the first set of brackets with the first term from the second set of brackets. In this case, we multiply x * x to get x^2.
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Multiply the outer terms together. The outer terms are the first term in the first set of brackets (x in our example) and the second term in the second set of brackets (-3). You can tell, because they are on the outside ends of the expression.x * -3 = -3xWe now have x^2 -3x.
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Multiply the inner terms together. The inner terms are the second term from the first bracket and the first term from the second bracket. Using our previous example, we get: 2 * x = 2xWe now have x^2 -3x +2x.
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Multiply the last terms together. The last terms are the second term from both the first and the second set of brackets. In this case, we get: 2 * -3 = -6We now have x^2 -3x +2x -6.
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Simplify the equation. Simplifying means combining like terms. In the above example, we have one pair of like terms: -3x and +2x. -3x +2x = -x. So we end up with:x^2 -3x +2x -6 =x^2 -x -6
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Tips & Warnings
Write clearly, and leave enough space between each character. Being able to see at a glance what you have written will make it easier to figure out math problems.
Remember negative signs when you multiply. x * -3 = -3x, not 3x. This is one of the most common mistakes people make when using the FOIL method.
