2023 AMC 10B Problems/Problem 22

Revision as of 14:02, 15 November 2023 by Technodoggo (talk | contribs) (Solution)

Solution (Quick)

A quadric equations can have up to 2 real solutions. With the $\lfloor{x}\rfloor$, it could also help generate another pair. We have to verify that the solutions are real and distinct.


First, we get the trivial solution by ignoring the floor. $(x-2)(x-1) = 0$, we get $(2,1)$ as our first pair of solutions.

Up to this point, we can rule out A,E.

Next, we see that $\lfloor{x}\rfloor^2-3x=0.$ This implies that $-3x$ must be an integer. We can guess and check $x$ as $\dfrac{k}{3}$ which yields $(\dfrac{2}{3},\dfrac{11}{3}).$

So we got 4 in total $(\dfrac{2}{3},1,2,\dfrac{11}{3}).$

~Technodoggo