Answer:
a
Step-by-step explanation:
given a quadratic equation in standard form
ax² + bx + c = 0 ( a ≠ 0 )
then the discriminant
Δ = b² - 4ac
• if b² - 4ac > 0 then 2 real solutions
• if b² - 4ac = 0 then 2 real and equal solutions
• if b² - 4ac < 0 then no real solutions
given
x² - 3x = - 4 ( add 4 to both sides )
x² - 3x + 4 = 0 ← in standard form
with a = b = - 3 , c = 4
then
b² - 4ac = (- 3)² - ( 4 × × 4) = 9 - 12 = - 3
since b² - 4ac < 0 then equation has no real solutions
Answer:
(A) 0.0039
Step-by-step explanation:
Problems of normally distributed samples can be 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:
The probability that the nitrite level is less than 2 ppm is 0.0918.
This means that when , Z has a pvalue of 0.0918. So when X = 2, Z = -1.33.
We use this to find
Which of the following is closest to the probability that on a randomly selected day the nitrite level will be at least 5 ppm
This is 1 subtracted by the pvalue of Z when X = 5. So
has a pvalue of 0.9961
1 - 0.9961 = 0.0039
So the correct answer is:
(A) 0.0039