Nếu log7x = 8log7ab2 – 2log7a3b (a, b > 0) thì x bằng
Giải thích
B
log7x = 8log7ab2 – 2log7a3b Û log7x = log7a8b16 – log7a6b2 = \({\log _7}\frac{{{a^8}{b^{16}}}}{{{a^6}{b^2}}} = {\log _7}{a^2}{b^{14}}\).
Suy ra x = a2b14.
B
log7x = 8log7ab2 – 2log7a3b Û log7x = log7a8b16 – log7a6b2 = \({\log _7}\frac{{{a^8}{b^{16}}}}{{{a^6}{b^2}}} = {\log _7}{a^2}{b^{14}}\).
Suy ra x = a2b14.