Select the product of (9x - 4)(3x + 9).

Question

Select the product of (9x - 4)(3x + 9).

27x2 - 69x - 36

96x - 36

27x2 + 69x - 36

12x + 5

Answer 1

For the problem as written, we get by F-O-I-L-ing,

 

(9x-4)(3x+9) = 27x² + 81x - 12x -36 = 27x² + 69x -36

Answer 2

FOIL Method

A technique for distributing two binomials. The letters FOIL stand for First, Outer, Inner, Last. First means multiply the terms which occur first in each binomial. Then Outer means multiply the outermost terms in the product. Inner means multiply the innermost two terms. Last means multiply the terms which occur last in each binomial. Then simplify the products and combine any like terms which may occur.



Example: (x + 2)(x + 5) = x·x + x·5 + 2·x + 2·5
First Outer Inner Last

= x2 + 7x + 10
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Please see the example above.  With your problem, (3x + 8)(3x - 8), just follow the same steps.

 

1)  Multiply 3x by 3x = 9x squared   (9x^2)

 

2)  Multiply 3x by -8 = -24x

 

3)  Multiply 8 by 3x =  24x

 

4)  Multiply 8 by -8 + = -64

 

Combine:

 

9x^2 -24x + 24x -64

 

The -24x and +24x cancel each other out

 

What's left is the following answer:

 

9x^2 - 64  (9x squared) - 64 

 

I meant to say 9x (squared) - 64  (I don't have the capability of writing in exponents in the standard form.)