nomer 5 gimana ya? (eksponensial)

^ tanda pangkat
{27^x / 9^y} = 81
{(3³)^x / (3²)^y} = 81
{3^3x / 3^2y} = 81
3^(3x - 2y) = 3^4
3x-2y = 4 |×2| => 6x-4y = 8 persamaan 1
5(25)^x = 3125^y
5¹.(5²)^x = (5^5)^y
5¹.5^2x = 5^5y
5^(1+2x) = 5^5y
1 + 2x = 5y
2x - 5y = -1 |×3| ==>6x-15y = -3 (persamaan 2)
eliminasi persamaan 1 dan 2
6x - 4y = 8
6x - 15y = -3
------------------- _
11x = 11
x = 1
2(1) - 5y = -1
- 5y = -1 - 2
y = -3/-5 = 3/5
3x + y = 3(1) + 3/5
= 3 + 3/5
= 15/5 + 3/5
= 18/5