Here are most of the reducible equations that we are likely to encounter. Begin by trying to identify what can be squared to obtain the leading variable term.

**Tip**: Look at the middle term for a hint as to what

*u*should be.

In the previous solved problem, we certainly could have distributed the expression on the left side, put the equation in standard form then re-factored it. Instead, here we are illustrating a technique that will be used to easily solve many other equations that are quadratic in form.

**Solve by making a**

*u*-substitution.**Solve**: x^6 + 26x^3 -27

**Six Answers**: { -3, 1, (3±3

*i*Sqrt(3))/2, (-1±

*i*Sqrt(3))/2 }

*u*-substitution. If the resulting quadratic equation does not factor, then use the quadratic formula.

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