Alan

If you meant the function to be f(x) = 2x^2 - 4x + 8 it's still a quadratic function mapping x on to f(x) and looks like this:

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It's just a quadratic function mapping x on to f(x):

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Probability of phone #1 not ringing = 1 - 0.89 = 0.11

Probability of phone #2 not ringing = 1 - 0.64 = 0.36

Hence probability of neither ringing (assuming the above probabilities are independent) = 0.11*0.36 = 0.0396

1 dm = 10cm   (dm - decimetre,  cm - centimetre)

So 8dm + 30cm =  110cm  (or 11dm)

As below:

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Solutions are:

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No problem; we all make mistakes.  This example shows that it's important to check your results wherever possible.

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.

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It is a graphing calculator, which is fairly easy to use. Like all these things it has good and bad features! 

Yes this is the right one Melody. It is free.