Here's a cool 0=2 proof I found.
Prove it wrong!
Wait, but you already defined b to be 2. Then how can it be 0 or 2?
No. 0 is just an extraneous root of the quadratic you synthesized.
Rom is right but it is good that you think about 'puzzles' like this.
You need to question the maths that is put in front of you.
Here is another example like your one
I can see that 9=(-3)^2 so I could say these fits the equation y=x^2
but there are two solutions to y=x^2 when y=9 x could be -3 or 3
They are just 2 different solutions to the equation that i synthesized.