Answer:
x = - 3 ± 3
Step-by-step explanation:
given the equation x² + 6x - 9 = 0
We can solve for x using the quadratic formula
x = ( - b ± ) / 2a
with a = 1, b = 6 and c = - 9
x = ( - 6 ± ) / 2
= ( - 6 ± ) / 2
= ( - 6 ± ) / 2
= ( - 6 ± 6 ) / 2
x = - 3 ± 3
Answer:
14.63% probability that a student scores between 82 and 90
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:
What is the probability that a student scores between 82 and 90?
This is the pvalue of Z when X = 90 subtracted by the pvalue of Z when X = 82. So
X = 90
has a pvalue of 0.9649
X = 82
has a pvalue of 0.8186
0.9649 - 0.8186 = 0.1463
14.63% probability that a student scores between 82 and 90