Answer:
third option
Step-by-step explanation:
Given
x² + 4x - 4 = 0 ( add 4 to both sides )
x² + 4x = 4
Using the method of completing the square
add ( half the coefficient of the x- term )² to both sides
x² + 2(2)x + 4 = 4 + 4, that is
(x + 2)² = 8 ( take the square root of both sides )
x + 2 = ± = ± 2
( subtract 2 from both sides )
x = - 2 ± 2
Answer:
(a) 0.119
(b) 0.1699
Solution:
As per the question:
Mean of the emission, million ponds/day
Standard deviation, million ponds/day
Now,
(a) The probability for the water pollution to be at least 15 million pounds/day:
= 1 - P(Z < 1.178)
Using the Z score table:
= 1 - 0.881 = 0.119
The required probability is 0.119
(b) The probability when the water pollution is in between 6.2 and 9.3 million pounds/day:
P(Z < - 0.86) - P(Z < - 1.96)
Now, using teh Z score table:
0.1949 - 0.025 = 0.1699