Question

Logaritmos!!!

Log2(x-5) + log2^7 = log2^21

Answer 1

$log_2(x-5)+log_2\ 7=log_2\ 21\\\\ log_2(x-5)+log_2\ 7-log_2\ 21=0\\\\ log_2\frac{(x-5)*7}{21}=0\\\\ 2^0=\frac{(x-5)*7}{21}\\\\ 1=\frac{(x-5)*7}{21}\\\\ (x-5)*7=21\\\\ 7x-35=21\\\\ 7x=21+35\\\\ 7x=56\\\\ x=\frac{56}{7}\\\\ \boxed{x=8}$