You aren't sharing much information (no directions??).
If your triangle is a right triangle AND 5x-1 and 4x+1 represent the lengths of the 2 shortest sides, then the Pyth. Theorem tells us that
(5x-1)^2 + (4x+1)^2 = (hypotenuse length)^2.
We know that this could not be an equilateral triangle, because 5x-1 differs from 4x+1.
This could be an isosceles triangle if the third side were either 5x-1 or 4x+1.
Please be more specific about what you're supposed to do here.