arlethgonzales10

08.07.2019 • 

Mathematics

Acompany has developed a new type of light bulb, and wants to estimate its mean lifetime. a simple random sample of 12 bulbs had a sample mean lifetime of 772 hours with a sample standard deviation of 67 hours. it is reasonable to believe that the population is approximately normal. find the lower bound of the 95% confidence interval for the population mean lifetime of all bulbs manufactured by this new process.

Ответ:

nique1024

15.01.2023

Mathematics

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Let's call the lesser number x and the other one x+8

Explanation:

The product x⋅(x+8)=240→

Or:  x2+8x=240→

We can rework this by subtracting 240 from both sides:

x2+8x−240=0

Now we factor −240 into two factors that add up to 8
After some trying we find 20and−12

The equation turns into

(x+20)(x−12)=0

→x=−20orx=12

So the pairs of numbers will be:

−20and−12 or +12and+20

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