# Perfect Square Trinomials

Like the difference of squares formula, perfect square trinomial formulas are very common on the GMAT.

For example, .

Note: In a perfect square trinomial, the middle term is twice the product of the square roots of the outer terms.

Example

If , then

1. â€“4
2. 4
3. 8
4. 16
5. 64
Solution

 by the formula by cubing both sides of the equation by the rule