Question

matlab 对数方程如何求解

solve('-0.51435*x+log10(x)=-1.74727','x')

Answer 1

把等号变成双等号即可：（下见代码）
>> syms x
>> solve(-0.51435*x+log10(x)==-1.74727,x)

ans =

-(20000*lambertw(0, -(10287*10^(1138194733825345/4503599627370496)*log(10))/2000000))/(10287*log(10))
－－－－－－－－－－－－－－－－－－－－－－－－－－－
（因为 [单等号] 只用来赋值，[双等号] 用来表达“相等”）

追问

solve('-0.51435*x+log10(x)==-1.74727','x')
??? Error using ==> solve at 77
' -0.51435*x+log10(x)==-1.74727 ' is not a valid expression or equation.
报错，这种写法不正确。

追答

你把引号去掉试试～
solve(-0.51435*x+log10(x)==-1.74727,x)

前后都不要加引号

追问

syms x
>> solve(-0.51435*x+log10(x)==-1.74727,x)
??? Error using ==> char
Conversion to char from logical is not possible.

Error in ==> sym.solve at 46
S{k} = char(varargin{k});
这是不用引号的结果