Ƙimar cikakkiya nisa ce

$\displaystyle 5-9 = -4$, me ya sa amsar $\displaystyle 4$ ce? A kan layin lambobi, ƙimar cikakkiya ita ce nisa tsakanin $\displaystyle 5$ da $\displaystyle 9$: matakai $\displaystyle 4$. Nisa ba ta taɓa zama mai debe ba.