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12. A student simplified [tex] \frac{x^{-1} y^3}{x y^{-2}} [/tex] as seen below. Is this student correct? If not, describe any errors.

[tex]
\begin{aligned}
\frac{x^{-1} y^3}{x y^{-2}} & = x^{-1+1} \times y^{3-(-2)} \\
& = x^0 y^5 \\
& = y^5
\end{aligned}
[/tex]

13. Johannes Kepler developed a formula to calculate the time it takes each planet to orbit the sun (called a period). The formula is:

[tex] T = 0.2 R^{\frac{3}{2}} [/tex]

where [tex] T [/tex] is the period in Earth days, and [tex] R [/tex] is the distance from the planet to the sun in millions of kilometers. Which planet has the longer period, Jupiter or Venus? By how long?



Answer :

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12. Analysis of Simplification:

We need to determine if the student's simplification of the expression [tex]\(\frac{x^{-1} y^3}{x y^{-2}}\)[/tex] is correct.

Let's follow the steps given by the student and analyze each one:

[tex]\[ \frac{x^{-1} y^3}{x y^{-2}} \][/tex]

Step 1: Combine the exponents of [tex]\(x\)[/tex] and [tex]\(y\)[/tex] in the numerator and denominator separately.

[tex]\[ = x^{-1-1} \times y^{3 - (-2)} \][/tex]

This step simplifies to:

[tex]\[ = x^{-2} \times y^{3+2} \][/tex]

[tex]\[ = x^{-2} \times y^5 \][/tex]

Step 2: Simplify the final expression.

[tex]\[ = \frac{1}{x^2} \times y^5 \][/tex]

So, the correct simplification should be:

[tex]\[ = y^5 x^{-2} \][/tex]

The student's solution was:

[tex]\[ x^{-1+1} \times y^{3-2} = x^0 y \Rightarrow y \][/tex]

From our correct simplification, we can see that the student made an error by incorrectly adding the exponents of [tex]\(x\)[/tex] in the numerator and denominator. Instead of combining the terms correctly, the student incorrectly simplified [tex]\(-1+1\)[/tex] and added the powers of [tex]\(y\)[/tex] as [tex]\(3-2\)[/tex] instead of [tex]\(3-(-2)\)[/tex].

Therefore, the correct final result is [tex]\( y^5 x^{-2} \)[/tex] not [tex]\( y \)[/tex], and the student was incorrect in this simplification.

13. Calculation of Orbital Period:

We are given Kepler’s formula:

[tex]\[ T = 0.2 R^{\frac{3}{2}} \][/tex]

where [tex]\(T\)[/tex] is the period in Earth days and [tex]\(R\)[/tex] is the distance from the planet to the sun in millions of kilometers.

Jupiter:
- [tex]\(R_{\text{Jupiter}} = 778.5\)[/tex] million kilometers

Calculating [tex]\(T_{\text{Jupiter}}\)[/tex]:

[tex]\[ T_{\text{Jupiter}} = 0.2 \times (778.5)^{\frac{3}{2}} \][/tex]

This gives us:

[tex]\[ T_{\text{Jupiter}} = 4344.281121773774 \text{ Earth days} \][/tex]

Venus:
- [tex]\(R_{\text{Venus}} = 108.2\)[/tex] million kilometers

Calculating [tex]\(T_{\text{Venus}}\)[/tex]:

[tex]\[ T_{\text{Venus}} = 0.2 \times (108.2)^{\frac{3}{2}} \][/tex]

This gives us:

[tex]\[ T_{\text{Venus}} = 225.09761153775045 \text{ Earth days} \][/tex]

Comparison:

To find which planet has the longer period, compare the periods of Jupiter and Venus.

[tex]\[ T_{\text{Jupiter}} = 4344.281121773774 \text{ days} \][/tex]

[tex]\[ T_{\text{Venus}} = 225.09761153775045 \text{ days} \][/tex]

Jupiter has the longer period.

Difference in Periods:

Calculate the difference in periods:

[tex]\[ \Delta T = T_{\text{Jupiter}} - T_{\text{Venus}} \][/tex]

[tex]\[ \Delta T = 4344.281121773774 - 225.09761153775045 \][/tex]

[tex]\[ \Delta T = 4119.183510236024 \text{ days} \][/tex]

Conclusion:

Jupiter has the longer period, and it is longer by 4119.183510236024 Earth days compared to Venus.