MHB Is this the simplified form of (a + b)^3 - 8c^3?

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The discussion focuses on factoring the expression (a + b)^3 - 8c^3 as a difference of cubes. Participants confirm that the expression can be rewritten as (a + b)^3 - (2c)^3. The difference of cubes formula is applied, leading to the factorization (a + b - 2c)((a + b)^2 + 2c(a + b) + 4c^2). Clarifications are made regarding the interpretation of -8c^3, emphasizing that it can be expressed as -(2c)^3. The conversation concludes with a consensus on the correct application of the difference of cubes formula.
mathdad
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Factor (a + b)^3 - 8c^3.

Is this the difference of cubes?

Formula:

x^3 - a^3 = (x - a)(x^2 + ax + a^2)

Let x = (a + b)

Let a = 8

(a + b - 8)((a + b)^2 + 8(a + b) + 64)

Correct?
 
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I would begin by writing the expression as the difference of cubes:

$$(a+b)^3-8c^3=(a+b)^3-(2c)^3$$

Now apply the difference of cubes formula...:D
 
Why did you write -8c^3 as -(2c)^3?

The number 8 is not part of c^3.

Are you saying that -8•c^3 = (-8c)^3?
 
RTCNTC said:
Why did you write -8c^3 as -(2c)^3?

The number 8 is not part of c^3.

Are you saying that -8•c^3 = (-8c)^3?

I applied the exponential property:

$$x^ny^n=(xy)^n$$

Since $8=2^3$, we can write:

$$8c^3=2^3c^3=(2c)^3$$
 
I got it now.
 
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