What is the value of x in the equation
1 answer:
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Answer:
x = - 3 ±
Step-by-step explanation:
x² + 6x + 7 = 0 ( subtract 7 from both sides )
x² + 6x = - 7
using the method of completing the square
add ( half the coefficient of the x- term )² to both sides
x² + 2(3)x + 9 = - 7 + 9
(x + 3)² = 2 ( take square root of both sides )
x + 3 = ± ( subtract 3 from both sides )
x = - 3 ±
Answer:
66.48% of full-term babies are between 19 and 21 inches long at birth
Step-by-step explanation:
Normal Probability Distribution:
Problems of normal distributions can be solved using the z-score formula.
In a set with mean and standard deviation
, the z-score 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 p-value, we get the probability that the value of the measure is greater than X.
Mean length of 20.5 inches and a standard deviation of 0.90 inches.
This means that
What percentage of full-term babies are between 19 and 21 inches long at birth?
The proportion is the p-value of Z when X = 21 subtracted by the p-value of Z when X = 19. Then
X = 21
has a p-value of 0.7123
X = 19
has a p-value of 0.0475
0.7123 - 0.0475 = 0.6648
0.6648*100% = 66.48%
66.48% of full-term babies are between 19 and 21 inches long at birth