有幾題F.4數學題想請教一下(急!!)20點

1.5^(-kx)=8
(5^x)^(-k) = 8
0.5^(-k) = 8
(2^(-1))^(-k) = 8
2^k = 8
2^k = 2^3
k = 3
2a) 3^(x+3) - 2(3^(x+2)) = 30 - 3^x
(3^3)(3^x) - 2(3^2)(3^x) = 30 - 3^x
9(3^x) = 30 - 3^x
3^x = 3
x = 1b)27(5^x)-125(3^x)=0
27(5^x) = 125(3^x)
27/125 = (3^x)/(5^x)
27/125 = (3/5)^x
(3/5)^3 = (3/5)^x
x = 3
3)f(-3x)．[f(x)^3] = k/8k(5/6)^(-3x) * k(5/6)^(3x) = k/8k² (5/6)^0 = k/8k² = k/88k² - k = 0k(8k - 1) = 0k = 0 (rejected) or k = 1/8
4)3^(x+1)-2^(y+1)=1-----(1)
4(3^x)+3(2^y)=24------(2)==>3(3^x) - 2(2^y) = 1 .....(1)
4(3^x) + 3(2^y) = 24 ..(2)(1)*3 + (2)*2 :9(3^x) + 8(3^x) = 3 + 48
3^x = 3
x = 1Sub it to (1) :3(3^1) - 2(2^y) = 1
2(2^y) = 8
2^y = 4
y = 2(x = 1 , y = 2)