A cube is shrunk so that its side lengths of 2x are reduced by 3 units. Using the Binomial Theorem, which of the following is the correct expression for the new volume of the cube? (2x−3)3 (1 point) Responses 8x3−36x2+54x−27 8 x cubed minus 36 x squared plus 54 x minus 27 8x3−36x2+54x+27 8 x cubed minus 36 x squared plus 54 x plus 27 8x3+36x2+54x+27 8 x cubed plus 36 x squared plus 54 x plus 27 8x3+36x2+54x−27

1 answer

To find the new volume of the cube after its side lengths are reduced, we start with the original side length of the cube, which is \(2x\). After the reduction, the new side length becomes \(2x - 3\).

We can use the Binomial Theorem to expand the volume of the cube:

\[ V = (2x - 3)^3 \]

According to the Binomial Theorem:

\[ (a - b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} (-b)^k \]

In our case, \(a = 2x\), \(b = 3\), and \(n = 3\). Thus, we apply the theorem:

\[ (2x - 3)^3 = \sum_{k=0}^{3} \binom{3}{k} (2x)^{3-k} (-3)^k \]

Let's calculate each term in the summation:

  1. For \(k = 0\): \[ \binom{3}{0} (2x)^3 (-3)^0 = 1 \cdot 8x^3 \cdot 1 = 8x^3 \]

  2. For \(k = 1\): \[ \binom{3}{1} (2x)^2 (-3)^1 = 3 \cdot 4x^2 \cdot (-3) = -36x^2 \]

  3. For \(k = 2\): \[ \binom{3}{2} (2x)^1 (-3)^2 = 3 \cdot 2x \cdot 9 = 54x \]

  4. For \(k = 3\): \[ \binom{3}{3} (2x)^0 (-3)^3 = 1 \cdot 1 \cdot (-27) = -27 \]

Now, we can put together all the terms:

\[ (2x - 3)^3 = 8x^3 - 36x^2 + 54x - 27 \]

Comparing this expression with the provided options, the correct expression for the new volume of the cube is:

\[ \boxed{8x^3 - 36x^2 + 54x - 27} \]