Answer:
Step-by-step explanation:
[tex]\text{rule }(x^a)(x^b)=x^{(a+b)}\\ \\ (b^{-7})(b^3)=b^{(-7+3)}\\ \\ b^{-4}=\frac{1}{b^4}[/tex]
1/ b^4
because -7 +3 = -4 but it can only be positive. So you but the -4 to the bottom to become b^4
