Answer for the blank is: 10
The exponents are -2, 3 and 9. Note how the bases are all the same at 4x. When we multiply exponential expressions like this, we add the exponents. So we'll get -2+3+9 = 1+9 = 10 as the final exponent over the base 4x
In short,
![(4x)^(-2)*(4x)^3*(4x)^9 =(4x)^(-2+3+9) = (4x)^(10)](https://img.qammunity.org/2021/formulas/mathematics/high-school/3svmxgu28u1wra59pi35ta6jek9uamgguq.png)