The half-life of Uranium-238 is 4.5 billion years. A 100 gram sample of the Uranium-238 sits in a cave, untouched, for 9 billion years. How much of the sample is left.

in counting the number of heads in 4 coin flips, the probability that we get exactly one head is the probability that we get anyone of the following 4 outcomes: httt, thtt, ttht, or ttth. each has probability 1/16, so the probability to get exactly one head in 4 flips is 1/16 + 1/16 + 1/16 + 1/16 = 4/16 = 1/4.

josh is incorrect

x= 7 and x= -1

step 2 is wrong and honestly first step is not needed, you just need to figure out the factors

i know its wrong because if you plug in the solutions josh found, they do not work (in the original equation)

x^2 -6x -7 = 0

(x-7) (x+1) = 0

x-7=0 x+1=0

x= 7 x= -1