The formula for an arithmetic sequence is given as;
[tex]\text{nth}=a+(n-1)d[/tex]The 5th term would be;
[tex]\begin{gathered} 5th=1.5+(5-1)(-0.75) \\ 5th=1.5+(4)(-0.75) \\ 5th=1.5-3 \\ 5th=-1.5 \end{gathered}[/tex]The 6th term would be;
[tex]\begin{gathered} 6th=1.5+(6-1)(-0.75) \\ 6th=1.5+(5)(-0.75) \\ 6th=1.5-3.75 \\ 6th=-2.25 \end{gathered}[/tex]