Jawabanmu

2014-07-27T10:26:43+07:00
11. {(1/25)^2n+6}^1/6 = 5^-4
{(1/5^-2)^2n+6}^1/6= 5^-4
{(5^-2)^2n+6}^1/6= 5^-4
(5^-4n-12)^1/6= 5^-4 (itu kan ada -4n-12 sama sama dibagi dgn 1/6 hasilnya -2/3n-2)
(5^-2/3n-2)= 5^-4
-2/3n-2= -4
-2/3n= -4+2
-2/3n= -2
n= -2÷-2/3
n= 3

12. 25^x²-5x+7= (1/25)^x-x²-15
(5^2)^x²-5x+7= (1/5^2)^x-x²-15
5^2x²-10x+14= (5^-2)^x-x²-15
5^2x²-10x+14= 5^-2x+2x²+30
2x²-10x+14= -2x+2x²+30
2x²-2x²-10x+2x+14-30= 0
-8x-16= 0
-8x= 16
x= -2

semoga membantu.. :)