Nothing changes if you don't add anything.
Example:
10+10=20
20+0=20
nothing changes.
There are 91 in total. Since there are 21 red cars, it would give you 21/91. Around a 23.07% chance.
I am pretty sure it is linear decrease,
If the polynomial is of the form x^2+bx+c (ie., no factor in front of the x^2!!) then you can look for numbers that add up to b and multiply to c.
So in this case: what two numbers, when added, give -2 and when multiplied, give 1? A little trial and error gives you -1 and -1.
So the factorization is (x-1)(x-1). This is zero for x=1. There is only one zero.
