Answer:
The bulbs should be replaced each 1436.9 hours.
Step-by-step explanation:
Problems of normally distributed samples are solved using the z-score formula.
In a set with mean
and standard deviation
, the zscore of a measure X is given by:

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
In this problem, we have that:

How often should the bulbs be replaced so that no more than 1% burn out between replacement periods?
This is the first percentile of hours. So it is X when Z has a pvalue of 0.01.
So it is X when Z = -2.33.




The bulbs should be replaced each 1436.9 hours.
Substitute x=9 and y=-2 into equation,
Left hand side=-2
Right hand side=1/3(9)+4= 3+4=7
Because LHS doesn’t = with RHS, the point (9,-2) doesn’t satisfy with the equation
Therefore the point doesn’t go through y=1/3x +4.
C - 7.6 = -4
c = -4 + 7.6
c = 3.6
Answer:


Step-by-step explanation:










