A traffic light at a certain intersection is green 50% of the time, yellow 30% of the time, and red 20% of the time. A car approaches this intersection once each day. Let X represent the number of days that pass up to and including the first time the car encounters a red light. Assume that each day represents an independent trial. Let Y denote the number of days up to and including the third day on which a red light is encountered. a. Find P(Y = 4).b. Find the mean of Y. c. Find the variance of Y.

e) none of the above because the measure of angle cba is 101°

answer: i ! the answer is   9000 seconds, also d

hope i

-lavira : )

x^2 + 81

we can factor this using difference of square binomials.

rewrite the equation:

x^2 - (-81)

factor:

(a^2 - b^2) = (√a^2 + √b^2)(√a^2 - √b^2)

(x^2 - (-81) = (x + √-81)(x - √-81)

we can remove the - from under the radical by multiplying it by i.

(x^2 - (-81) = (x + i√81)(x - i√81)

(x^2 - (-81) = (x + 9i)(x - 9i)

we can check our answer by using foil:

x^2 - 9ix + 9ix - 81i^2

x^2 - 81^2

i^2 = -1

x^2 + 81