Posted by **Brady** on Friday, February 14, 2014 at 9:52pm.

I will appreciate it if anyone can help me with the following:

1. The optimal height h of the letters of a message printed on pavement is given by the formula . Here, h= (0.00252d^(9/4))/e d is the distance of the driver from the letters and e is the height of the driver’s eye above the pavement. All of the distances are in meters. Explain how to find h when d = 90 m and e = 1.4 m.

2.Simplify.

(27a^(-6) )^(-2/3)

For 2 I got 1/(9a^4 )as my answer, but can someone again please check this.

For 1 I think the answer is:

First, you replace the variables with 90 and 1.4 to get this equation: (0.00252∙〖90〗^(9/4))/1.4. Next, you turn the 〖90〗^(9/4)into ∜(〖90〗^9 ). Then, I turn ∜(〖90〗^9 )into 3∜(〖10〗^9 ), and simplify 3∜(〖10〗^9 )to 9∜10. Next, I divide o.oo252 by 1.4 to get 0.0018. Then, my next equation is: 0.0018∙9∜10. Finally, I multiply 0.0018 and 9 together to get 0.0162, and my final answer is 0.0162∜10.

If anyone can answer or help me for these two problems, please do. I will appreciate it even more if you can answer and/or check the problems as soon as possible. I have been waiting and trying to answer it for a long time. My mom wants me to get my lesson done on this topic today, and I am stuck at this point, which is really close to the end. I am willing to go step by step for each one until I get the right answer. Also, thank you if anyone can help or answer these two problems.

- Rational Exponents - Please Help!!!! -
**Ms. Sue**, Friday, February 14, 2014 at 10:09pm
Perhaps you need a personal tutoring session with your instructor.

- Rational Exponents - Please Help!!!! -
**Steve**, Friday, February 14, 2014 at 10:42pm
#1 (0.00252d^(9/4))/e

= (0.00252*90^(9/4))/1.4

90^(1/4) = ∜90 = 3.0801

90^(9/4) = 3.0801^9 = 24948.5693

So, we now have

0.00252 * 24948.5693 / 1.4 = 44.9074

If you visit wolframalpha.com you can play around with arbitrarily complex expressions, just to see how things combine.

You went wrong starting here:

Then, I turn ∜(〖90〗^9 )into 3∜(〖10〗^9 )

Where did that 3 come from?

∜(〖90〗^9 ) = ∜(90^8 * 90) = 90^(8/4) * ∜90 = 90^2 * ∜90 = 8100∜90

You seem to lose track of the pieces when factoring stuff out.

#2

(27a^(-6) )^(-2/3)

27^(-2/3) * a^(-6 * -2/3)

1/9 a^4

a^4 / 9

- Rational Exponents - Please Help!!!! -
**Brady**, Monday, February 17, 2014 at 3:23pm
Thank you Steve. I will try to do better during these type of problems, I will even do it your way. Thank you again!

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