math
posted by help .
I have solved the following questions, let me know if they are correct, thanks.
1. Simplify, and write in the base of 3: (9^x . 3^4x)^2
answer: 3^12x
2. Differentiate and simplify
a. y= 3x^4  4e^x + 8
answer: 4(3x^3  e^x)
b. y= (3 + 4e^x)^5
answer: 20e^x (3+ 4ex)^4
c. y= (e^x  1) / x^2
answer: (xe^x  2e^x +2) / x^3

All correct.