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You've been chosen to practice football with Odell! On the day of the practice, you leave your house at 3 AM, but due to heavy traffic, arrive at 5:23 AM. Odell noted that it took you \(x^4-2x^3+8x+127\) minutes to get to practice, for a positive integer  You finish practice at 3 PM, and traffic is still quite nasty- taking you \(x^6-8x^3+x^2-2x+12\) minutes to get home. At what time do you arrive home?

 Mar 25, 2016

Best Answer 

 #2
avatar+33616 
+5

Time taken in the morning is 143 minutes, so:   \(x^4-2x^3+8x+127=143\)

 

Rewrite this as;  \(x^4-2x^3+8x-16=0\)

 

This factors as:  \((x-2)(x+2)(x^2-2x+4)\)

 

The only real positive solution is x = 2.

 

According to the equation you have for the return journey, time taken = \(2^6-8*2^3+2^2-2\times 2+12\rightarrow 12\)  minutes!

 

This doesn't square with heavy traffic!!   I think you might have written the second equation incorrectly.

.

 Mar 27, 2016
 #1
avatar+425 
+5

Duration from 3 AM to 5.23 AM -> 2 h 23 min = 83 min

 

I use PhotoMath (best calculator)

 

Solving for x,

 

(x4 - 2x3 + 8x + 127 ) min = 83 min

 

Subtract 127.

 

x4 - 2x3 + 8x = -44

 

Expand the algebraic expression

 

x*x*x*x - 2*x*x*x + 8*x = -44

 

Simplify

 

Properties: Distributive property of subtraction/multiplication : (a-b)c = ac - bc

 

(x-2)x*x*x + 8*x = -44

 

.

.

.

 

By using photo math, we found out that x could be one of the following:

 

x = -1.464914 ± 1.490055 i  Option 1 + Option 2 -

x = 2.464914 ± 2.000378 i  Option 3 + Option 4 -

 

Options 1 and 2 will yield -34 minutes - nonsense.

Options 3 and 4 yielded -470 minutes - nonsense too.

 

IDK if this makes sense...

 Mar 27, 2016
 #3
avatar+425 
0

Sorry, I made a calculation error in the first step.

MWizard2k04  Mar 31, 2016
 #2
avatar+33616 
+5
Best Answer

Time taken in the morning is 143 minutes, so:   \(x^4-2x^3+8x+127=143\)

 

Rewrite this as;  \(x^4-2x^3+8x-16=0\)

 

This factors as:  \((x-2)(x+2)(x^2-2x+4)\)

 

The only real positive solution is x = 2.

 

According to the equation you have for the return journey, time taken = \(2^6-8*2^3+2^2-2\times 2+12\rightarrow 12\)  minutes!

 

This doesn't square with heavy traffic!!   I think you might have written the second equation incorrectly.

.

Alan Mar 27, 2016

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