Question

Resolva a equação $3 . ( 3^{x+4} ) = 81$

a  x = 2
b  x = 3
 c x = -5
d  x = 1
e  x = -1

Answer 1

$3*(3^{ x+4 })=81\\ 3^{ 1 }*3^{ x+4 }=81\\ 3^{ x+5 }=3^{ 4 }\\ x+5=4\\ x=4-5\\ x=-1$

Answer 2

$3 . ( 3^{x+4}) = 81$
$log[3 . ( 3^{x+4})] = log81$
$log3 + log( 3^{x+4}) = log( 3^{4} )$
$log3 + (x + 4)log3 = 4log3$
$(x + 4 + 1)log3 = 4log3$
$(x + 5)log3 = 4log3$
$(x + 5) = \frac{4log3}{log3}$
$x + 5 = 4$
$x = 4 - 5$
$x = - 1$

Portanto, alternativa E