Answer:
- doing the inverse operation
Explanation:
You can tell how to isolate a variable by listing the operations done to it, as prescribed by the order of operations. Then, you work backwards up the list performing inverse operations as you go.
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Additional comment
Where mixed powers of the variable are involved, as in polynomials of degree higher than 1, there is generally not an inverse operation you can use to isolate the variable. Rather, special forms are used that facilitate isolating the variable. The variable in a quadratic, for example, can be isolated by "completing the square." Similar procedures are available for solving cubic and quartic equations, though those tend to be somewhat more complicated.
There are many kinds of equations in which there are no methods for isolating the variable. In general, any mix of polynomial terms and logarithmic, exponential, or trigonometric function terms are in that category: x +sin(x) -3 = 0, for example. (A graphing calculator shows the solution is near x=2.18, where the angle is in radians.)