Question

Solve this equation log3X + log3(x-6) = log3 7

Answer 1

Hello!

log₃(x) + log₃(x - 6) = log₃(7) <=>

<=> log₃(x * (x - 6)) = log₃(7) <=>

<=> log₃(x² - 6x) = log₃(7) <=>

<=> x² - 6x = 7 <=>

<=> x² - 6x - 7 = 0 <=>

<=> x² + x - 7x - 7 = 0 <=>

<=> x * (x + 1) - 7 * (x + 1) = 0 <=>

<=> (x + 1) * (x - 7) = 0 <=>

<=> x + 1 = 0 and x - 7 = 0 <=>

<=> x = -1 and x = 7, x ∈ { 6; +∞ } <=>

<=> x = 7

Good luck! :)