Question

Is -2/5 a rational number?

Answer 1

yes it is a rational in p/q form numerator can be negative

Answer 2

A rational number is any number which can be represented in the form of a fraction $\frac{x}{y}$, irregardless of it being positive or negative. So, this number you have given is already in fractional form and so it is rational. In addition, irrational numbers never end if you expand the fractional form,i.e. 22/7 goes on and on. If you convert  -2/5 into decimal it is -0.4 and so it is rational.