This is the quadratic formula.
Answer:
Step-by-step explanation:
answer :C
Answer:
a)
And we can find this probability with the complement rule:
b) 
And if we use the z score we got:
Step-by-step explanation:
Let X the random variable that represent the lengths of a population, and for this case we know the distribution for X is given by:
Where
and
Part a
We are interested on this probability
And we can use the z score formula given by:
And using this formula we got:
And we can find this probability with the complement rule:
Part b
For this case we select a sample of n =44 and the new z score formula is given by:

And if we find the z score we got:

And if we use the z score we got:
Answer:
4. x= 18
Step-by-step explanation:
We solve the problem like this:
Since 3 is proportional to 6 and 9 is proportional to x, we set up a proportion.
3/9 = 6/x
We then use cross-multiplication to solve for x.