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Which of the following shows the extraneous solution to the logarithmic equation log Subscript 7 Baseline (3 x cubed + x) minus log Subscript 7 Baseline (x) = 2 x = negative 16 x = negative 4 x = 4 x = 16

Answer :

sqdancefan

Answer:

  • x = -4

Step-by-step explanation:

A graphing calculator shows there is one solution to ...

  [tex]\log_7{(3x^2+x)}-\log_7{(x)}=2[/tex]

However, the usual solution method would be to combine the logarithms and take the antilog to get ...

  [tex]\log_7{\left(\dfrac{3x^3+x}{x}\right)}=2\\\\\log_7{(3x^2 +1)}=2\\\\3x^2+1=7^2\\\\x^2=\dfrac{49-1}{3}=16\\\\x=\pm 4\qquad\text{take the square root}[/tex]

This gives two solutions. the "solution" x = -4 is extraneous, as it doesn't work in the original equation. "x" must be positive in the log expressions.

${teks-lihat-gambar} sqdancefan
grandmateeth

Answer:

x = - 4

Step-by-step explanation:

Got it right :)

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