Probability › Coins › Equal numbers of heads

Coin flips moving two numbers together

High school · ●●●○○ 50 pts

Steph and Jeff each start with the number 4, and Travis is flipping a coin. Every time he flips heads, Steph replaces her number xx with 2x−12x-1, and Jeff replaces his number yy with y+8y+8. Every time he flips tails, Steph replaces her number xx with x+12\frac{x+1}{2}, and Jeff replaces his number yy with y−3y-3. After some (positive) number of coin flips, Steph and Jeff end up with the same number, which is below 2012. How many times was the coin flipped?

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invariantsexponential equationsdivisibilityrecurrence relationsinduction