Question 131197
let x="number of players" __ each player plays x-1 matches BUT a vs b is the same as b vs a
__ so the number of matches is x(x-1)/2


x(x-1)/2=45 __ multiplying by 2 and subtracting 90 __ x^2-x-90=0


factoring __ (x+9)(x-10)=0 __ x+9=0 and x-10=0