# Rules (Binomial)

These rules are necessary in many instances. The formulas can also be found in the book of tables, but it is good to learn and identify when the formula can be used and how it works.

### Square of binomial (perfect square trinomials)

The binomial rule above is easy to outline with geometry. Below, on the other hand, if we subtract the bars* ab* from the square *a,* the square of* b* must be added because the corner is subtracted twice.

It is good to note here the difference in raising the product by a power . We cannot directly raise the terms inside parentheses by the power and add them up. In this case, you should start by multiplying the open parentheses first**.**

**Example 1**

### Difference of squares

When the sum and the difference is multiplied, only the squares remain. Other terms simplify to zero.

**Example 2**

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