Which of the following responses shows that polynomials form a closed system

under multiplication?(1 point)
$\frac {3x^{2}}{4-1}$
$(x)(\frac {1}{2}x)$
$(\sqrt {x})(6x\cdot -3)$
. $\frac {1}{4x^{3}}\cdot 5$

3 answers

To determine if polynomials form a closed system under multiplication, we need to analyze the responses given to verify whether they result in polynomials.

  1. Response: \(\frac{3x^{2}}{4-1}\)

    Simplifying this expression, we have: \[ \frac{3x^{2}}{4-1} = \frac{3x^{2}}{3} = x^{2} \] This is a polynomial.

  2. Response: \((x)(\frac{1}{2}x)\)

    Multiplying these terms, we get: \[ (x)(\frac{1}{2}x) = \frac{1}{2}x^2 \] This is also a polynomial.

  3. Response: \((\sqrt{x})(6x\cdot -3)\)

    First, simplify \(6x \cdot -3\): \[ 6x \cdot -3 = -18x \] Now multiplying \(\sqrt{x}\) and \(-18x\): \[ (\sqrt{x})(-18x) = -18\sqrt{x} \cdot x = -18x^{3/2} \] This is not a polynomial since \(\sqrt{x} = x^{1/2}\) has a fractional exponent.

  4. Response: \(\frac{1}{4x^{3}} \cdot 5\)

    Simplifying this gives: \[ \frac{5}{4x^{3}} = \frac{5}{4}x^{-3} \] This is not a polynomial because it has a negative exponent.

From the above analysis, we see that only the first two responses yield polynomials. However, since the third and fourth responses result in non-polynomial expressions, we conclude that polynomials do not form a closed system under multiplication.

The responses show that:

  • The first two are polynomials,
  • The third and fourth are not.

Thus, the conclusion is that polynomials are not closed under multiplication based on the given options.

Pick one of the answers

The response that shows polynomials form a closed system under multiplication is:

\((x)(\frac{1}{2}x)\)

This results in \(\frac{1}{2}x^2\), which is a polynomial.