2.5^{-4r}=6.4

解答

2. 5^{- 4 r} = 6.4

r = - \frac{ln ( 6.4 )}{4 ln ( 2.5 )}

十进制

r = - 0.50647 \dots

求解步骤

2. 5^{- 4 r} = 6.4

使用指数运算法则

- 4 r ln (2.5) = ln (6.4)

解

- 4 r ln (2.5) = ln (6.4) : r = - \frac{ln ( 6.4 )}{4 ln ( 2.5 )}

r = - \frac{ln ( 6.4 )}{4 ln ( 2.5 )}

x^{l o g_{10} (x)} = 1 0^{8}

9^{x} + 9 = 10 \cdot 3^{x}

6^{3 x - 5} = 27

5 (2^{x - 3}) = 4 (3^{x + 4})

8^{x} + 8^{x - 1} + 8^{x + 1} = 292