Urn 1 contains 4 blue tokens and 9 red tokens; urn 2 contains 12 blue tokens and 5 red tokens. You flip a coin twice and if you see head two times, then you pick urn 2 else (if you see at least once the tail) you pick urn 1 and draw out a token at random from that urn. Given that the token is blue, what is the probability that the token came from urn 2

x = ±sqrt(10)

step-by-step explanation:

5 - 2x² = -15

subtract 5 from each side

5-5 - 2x² = -15-5

-2x^2   = -20

divide by -2 on each side

-2x^2   /-2= -20/-2

x^2 =10

take the square root on each side

sqrt(x^2 )=±sqrt(10)

x = ±sqrt(10)

check:

5 - 2x² = -15

+sqrt(10)

5 - 2(sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

-sqrt(10)

5 - 2(-sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15