help please !! solve for x using the method of common bases.

Question

1) 3^2x=84

2)125^x=(1/25)^4-x

Answer 1

#2)

(5^3)^x = (5^(-2))^(4-x)

so (3x) = -2(4-x)

3x = -8 + 2x

x = -8

125^(-8) = 1/125^8 = (1/5)^24

(1/25)^12 = (1/5)^24

#1) there is not common base: 84 = 2*42 = 2*2*21 = 2*2*3*7

2x * log 3 = log(84) = log(2^2 *3*7)

2x * log 3 = 2 log 2 + log3 + log 7

x = (2 log 2 + log 3 + log 7)/ (2 log 3)