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

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Discussion Overview

The discussion revolves around the simplification and factoring of the expression \((a + b)^3 - 8c^3\). Participants explore whether this expression can be treated as a difference of cubes and apply relevant formulas to factor it.

Discussion Character

  • Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant suggests factoring \((a + b)^3 - 8c^3\) as a difference of cubes using the formula \(x^3 - a^3 = (x - a)(x^2 + ax + a^2)\), proposing \(x = (a + b)\) and \(a = 8\).
  • Another participant agrees with the difference of cubes approach but rewrites \(8c^3\) as \((2c)^3\) to apply the formula.
  • A participant questions the rewriting of \(-8c^3\) as \(-(2c)^3\), seeking clarification on whether this transformation is valid.
  • A later reply defends the transformation by referencing the exponential property and explaining that \(8c^3\) can be expressed as \((2c)^3\) since \(8 = 2^3\).
  • One participant indicates understanding after the clarification regarding the transformation of \(8c^3\).

Areas of Agreement / Disagreement

Participants express differing views on the validity of rewriting \(-8c^3\) as \(-(2c)^3\), indicating a lack of consensus on this specific transformation.

Contextual Notes

Some assumptions about the properties of exponents and the application of the difference of cubes formula are discussed, but the discussion does not resolve whether the transformations are universally accepted.

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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