The third term is 6a²b²
Explanations:The given expression is:
[tex]\begin{gathered} (a-b)^4 \\ \end{gathered}[/tex][tex]\begin{gathered} (a-b)^4=4C0a^4(-b)^0+4C1a^3(-b)^1+4C26a^2(-b)^2+4C3a(-b)^3+4C4(-b)^4 \\ (a-b)^4=a^4-4a^3b+6a^2b^2-4ab^3+b^4 \end{gathered}[/tex][tex]\text{The third term in the expansion is 6a}^2b^2[/tex]