-9(x + 3) - 6(3x - 6)(3x + 6)

Question

having trouble collecting the like terms

Answer 1

Not quite D. Y.

 

-9(x+3)-6(3x+6)(3x-6)=?

 

Taking it in baby steps:

 

Step 1: (3x-6)(3x+6)= (3x times 3x)+ (3x times+6)+ (3x times -6)+ (6 times -6)= 9x^2+18x-18x-36=9x^2-36

 

Step 2: now deal with -6(9x^2-36)= (-6 times 9x^2)-(-6 times -36)= -54x^2+216

 

Now Step 3: -9(x+3)= -9x-27

 

Step 4: You are left with -9x-27-54x^2+216, combine like with like then put in order which gives you -9x+ (-216+27)-54x^2= -9x-189-54x^2 which in order: -54x^2-9x+189 and you can reduce each by -9 so it becomes (-9)(6x^2+x-21)

Answer 2

Hello, Shazai

 

Lets do this in stages

-9(x+3)= -9x -27

 

Next, let's do the special case 

(3x-6)(3x+6)= (3x)(3x)+ (3x)(6) -(6)(3x)-(6)(6)

                      9x^2+ 18x -18x -36

                      9x^2-36

 

There is -6 in front of this, so we have

-6[9x^2-36]= -54x^2 + 216

 

putting all together, 9x^2-9x+216-36

                              9x^2-9x+180

There you have...

I hope this helps, and please rate my answer :)

 

D.Y. Taylor