Solve the logarithmic equation. Be sure to reject any value that is not in the domain of the original logarithmic expressions. Give the exact answer. log6x2 = log6(5x + 36)

Respuesta :

[tex]\bf log_6(x^2)=log_6(5x+36)\impliedby \textit{removing the logs} \\\\\\ x^2=5x+36\implies \begin{array}{lcclll} x^2&-5x&-36&=0\\ &\uparrow &\uparrow \\ &-9+4&-9\cdot 4 \end{array} \\\\\\ (x-9)(x+4)=0\implies x= \begin{cases} 9\\ -4 \end{cases}[/tex]

domain for a logarithm is that, the value of the expression has to be positive, logarithms will never use a negative value, so in this case, both cases provide a positive value

Answer:x=-4 or 9

Step-by-step explanation:

Given

[tex]log_{6}( x^2)=log_{6}(5x+36)[/tex]

This log will be defined when

5x+36>0

[tex]x>-\frac{36}{5}[/tex]

L.H.S=R.H.S

thus [tex]x^2=5x+36[/tex]

[tex]x^2-5x-36=0[/tex]

[tex]x^2-9x+4x-36=0[/tex]

[tex]\left ( x+4\right )\left ( x-9\right )=0[/tex]

thus x=-4 or 9

as these two values are in the domain therefore -4 & 9 are the solution of the Given system.