Since she has seven key the probability that the first one will open the door is

if it takes three attempts to open the door,the probability is

if the three attempts would not work
then the probability that the fourth attempt will open the door is

hope this helps
Yes
factor out the 2z^2 in each term
(2z^2)(z^2-5z+4)
factor some more
z^2-5z+4
find what 2 numbers multiply to get 4 and add to get -5
the numbers are -1 and -4
(z-1)(z-4)
the factored form is
(2z^2)(z-1)(z-4)
Step-by-step explanation:
use herons formula
√s(s-a)(s-b)(s-c)
where s is the semi perimeter
S=20
and a,b,c are sides of triangle
=√20(20-17)(20-9)(20-14)
=√20.3.11.6
=62.92
nearest whole number is 63
option B is correct
the answer is 4
just think of -4 as 4 in this question it is looking for the one closer and now that both of them are counting numbers 4 is less
2/9=0.222.....
it is alot closer to zero than any of ther other numbers