# How do you factor the expression #64x^2 + 81#?

##### 3 Answers

#### Answer:

#### Explanation:

If

As a result

We can do something with Complex coefficients...

First notice that

The difference of squares identity can be written:

#a^2-b^2 = (a-b)(a+b)#

The *imaginary unit*

Hence we find:

#64x^2+81#

#=(8x)^2+9^2#

#=(8x)^2-(9i)^2#

#=(8x-9i)(8x+9i)#

If we want to, we can write a "sum of squares" identity:

#a^2+b^2 = (a-bi)(a+bi)#

#### Answer:

(there are no factors with only Real components)

#### Explanation:

Remember that

If there were any factors with only Real components the equation

however we can tell from the fact that the discriminant