To solve equations for the unknown, use inverse operations to isolate the variable. These inverse operations ‘‘undo’’ what has been done to the variable. That is, inverse operations are used to move quantities across the equal sign. For instance, in the equation 5x = 10, x is multiplied by 5, so to move 5 across the equal sign, you need to ‘‘unmultiply’’ the 5. That is, divide both sides of the equation by 5 (equivalently, multiply each side of the equation by 1/5). In the equation 5 + x = 10, to move 5 across the equal sign, you must ‘‘unadd’’ 5. That is, subtract 5 from both sides of the equation (equivalently, add –5 to both sides of the equation).
In short, what is added must be subtracted; what is
subtracted must be added; what is multiplied must be divided; and what is
divided must be multiplied. There are other operation pairs (an operation and
its inverse); some will be discussed later.
In much of this book, when the coefficient of x (the number
multiplying x) is an integer, both sides of the equation will be divided by
that integer. And when the coefficient is a fraction, both sides of the
equation will be multiplied by the reciprocal of that fraction.
Examples
Practice
Solutions
“Sumber Informasi”
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