factoring and solving polynomial equations: 8x^3 - 27 = 0

[justjoz]

Alright, the problem goes like this, but I KNOW it's wrong, can anyone help me by telling me where I went wrong?

8x^3=0
92x+3)(4x^2+6x+9)=0
x=3/2

 

[justjoz]

I goofed on that equation, it's supposed to be

8x^3 - 27 = 0
( 2x + 3 ) ( 4x^2 + 6x + 9 )
x= 3/2

 

[tkhunny]

...or not.

s/b 2x-3

(+3)*(+9) = (+27) No good.

 

[stapel]

8x^3 - 27 = 0
( 2x + 3 ) ( 4x^2 + 6x + 9 )

You might want to review the sum- and difference-of-cubes formulas, as you appear to have memorized them incorrectly.

Eliz.