若(m+1/2)²+∣n+1∣=0 ,因(m+1/2)²≥0 ∣n+1∣≥0
故(m+1/2)²=0 ∣n+1∣=0 得：m= -1/2,n= -1
所以：5m²*n³+4(m-n) = 5/4 * (-1) + 4*(1/2) = 3/4