Question

超越方程求解和多项式化简3^(-x+9)=2^(-5x),x=?(用10为底的对数表示）(20x+5x^2)/(5-x)

Answer 1

3^(-x+9)=2^(-5x)

3^(-x) * 3^9 = (2^5)^(-x)

3^(-x) * 19683 = 32^(-x)

(3/32)^x = 19683

x lg(3/32) = lg(19683)

x = lg(19683) / lg(3/32)

(20x+5x^2)/(5-x)

= 5x * (4+x)/(5-x) .不能再约分了,就不能化简了